一、为嘛子要学习Springboot

二、简单的说下springboot

三、咱们对比看看呗

四、开始操作，建项目

1、建一个maven项目

2、pom.xml 依赖以及配置文件

①简单的依赖如下，我就不细说了

②配置文件，application.yml

3、创建相应的包结构

4、使用 Mybatis Generator 自动生成实体类、mapper和mapper.xml文件

5、填写各个包的内容

①mapper 增加一个方法

②mapper.xml 的写法

③service 层接口的编写

④service 的 Impl 实现类

⑤Controller 层

五、运行

六、遇到的问题以及解决方案

1、刚建好项目，啥都没干呢就看到 index.jsp 红叉，如下：

错误状况：

解决方案：

2、项目基本写完，没看到红叉之类的错误提示，但是一运行，报错

错误状况：

小小分析：

解决方案：

3、再次运行，又报错了，

错误状况：

查找问题：

定位到问题发生位置后，百度解决：

4、Application run failed 启动失败

小小分析：

解决方案：

5、启动已经没问题，但是控制台有一个警告

警告详情：

问题所在：

解决问题：

一、为嘛子要学习Springboot

Springboot已经成为基本技能要求的基本。我不知道这样说语言能通不，只是看到现在各种招聘什么的，基本要求都是分布式、微服务、springboot、springcloud、redis、消息中间件等。就算有的招聘上还写的SSM等，到时候面试的时候问用过什么框架啥的。问完，你只用过ssm或ssh，他也会问你对于springboot、springcloud等是否有经验。很多地方，一听，不会cloud基本就pass掉你。所以，看起来springcloud已经成为必会的基本技能，而学习springcloud，你就抛不开springboot的使用，毕竟springboot建立项目确实快。

二、简单的说下springboot

简单粗暴的说，springboot就是让你建项目和使用插件等简单很多很多，让你更快更便捷的建立一个项目，减少你在配置上浪费的时间。

打个比方，就像你要吃饭，过去的吃饭，就得准备各种食材调料，按一定的顺序或者说手法等去处理和调配他们，让他们成为能够下咽的几个菜。而springboot就像你有点钱了，下馆子了，去到饭店，一看菜单，嗯~有套餐，就给服务员说，来个AAA套餐，你不用说要什么菜，也不需要知道这些菜有什么食材和调料。反正付了钱直接吃就是了。

约定大于配置，化繁为简，他把很多东西都给你弄好了，有默认的一套，你用就行了。

当然喽，springboot可不止这一个特点，它可以热部署、内嵌Servlet容器、自动装配、自带应用监控等等，对于学霸或者说有上进心的人来说，这些都要去了解，不过我这种渣渣，当然主要是咋个用喽。

三、咱们对比看看呗

咱们先看下以前的ssm项目，

看到这么多的 .xml 文件有没有很开心？开心到想砸了眼前的东西

好像说了很多废话，还是开始建项目吧

四、开始操作，建项目

听说eclipse有创建Springboot的插件sts。我没装，所以还是maven创建吧

1、建一个maven项目

File→New→Maven Project

直接Next

选择webapp

填写下图剪头指示的框框，然后Finish

创建好了，项目结构如下图

此时为空的maven项目，我们先把pom.xml引用了好依赖，再在相应的包在 src/main/java 中建好

2、pom.xml 依赖以及配置文件

①简单的依赖如下，我就不细说了

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.lx</groupId><artifactId>springboot_demo</artifactId><packaging>war</packaging><version>0.0.1-SNAPSHOT</version><name>springboot_demo Maven Webapp</name><url>http://maven.apache.org</url><!-- 依赖父类springboot版本 --><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.3.1.RELEASE</version></parent><!--springmvc的依赖--><dependencies><!--web相关--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!--添加springdatajpa的依赖--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId></dependency><!--数据库驱动包--><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId></dependency><!--springBoot整合Mybatis依赖--><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>2.1.3</version></dependency><!--测试依赖--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><!--阿里数据库连接池 --><dependency><groupId>com.alibaba</groupId><artifactId>druid-spring-boot-starter</artifactId><version>1.2.6</version></dependency><!--aop支持--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-aop</artifactId></dependency><dependency><groupId>org.mybatis.generator</groupId><artifactId>mybatis-generator-core</artifactId><version>1.3.5</version></dependency></dependencies><build><finalName>springboot_demo</finalName><resources><resource><directory>src/main/resources</directory><includes><include>**/*.properties</include><include>**/*.yml</include><include>**/*.xml</include></includes></resource><resource><directory>src/main/java</directory><includes><include>**/*.properties</include><include>**/*.yml</include><include>**/*.xml</include></includes><filtering>true</filtering></resource></resources><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId><executions><execution><!--打包时，重新打包指定spring boot的启动类 --><id>repackage</id><goals><goal>repackage</goal></goals></execution></executions></plugin><plugin><!--Mybatis-generator插件,用于自动生成Mapper和POJO--><groupId>org.mybatis.generator</groupId><artifactId>mybatis-generator-maven-plugin</artifactId><version>1.3.5</version><!--插件设置--><configuration><!--允许移动生成的文件--><verbose>true</verbose><!--启用覆盖--><overwrite>true</overwrite><!--自动生成配置 如果名字是generatorConfig.xml可以省略配置<configurationFile>src/main/resources/generatorConfig.xml</configurationFile>--></configuration></plugin></plugins></build>
</project>

②配置文件，application.yml


server:port: 8080
spring:datasource:#驱动driver-class-name: com.mysql.jdbc.Driverurl: jdbc:mysql://xxx.xxx.xxx.xxx:3306/xxxxxx?characterEncoding=utf8username: rootpassword: *********#连接池类型type: com.alibaba.druid.pool.DruidDataSourcedruid:# 最小数min-idle: 5# 最大数max-active: 20# 初始大小initial-size: 5# 配置获取连接等待超时时间max-wait: 6000# 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫秒time-between-eviction-runs-millis: 60000# 配置一个连接在池中最小生存时间  单位为毫秒min-evictable-idle-time-millis: 300000validation-query: SELECT 1 FROM DUALtest-while-idle: truetest-on-borrow: falsetest-on-return: false# 打开 PSCache，并且指定每个连接上PSCache的大小pool-prepared-statements: truemax-pool-prepared-statement-per-connection-size: 20# 配置监控统计拦截的filters，去掉后监控界面sql无法统计，wall用于防火墙filters: stat,wallmybatis:# model的包type-aliases-package: com.lx.springboot_demo.modelconfiguration:# 开启驼峰uName自动映射到u_namemap-underscore-to-camel-case: true#  该配置项配置了MyBatis配置文件保存路径mapper-locations: classpath:mappers/*.xml
#  配置扫描对应实体所在包,将mapper的实现类注入容器我们在启动器类上加了@MapperScan注解这里就不需要了

3、创建相应的包结构

选择 src/main/java 反键 New → Package

填写Name 然后完成

把这个Java文件改为启动类

名字看你自己哦，我这是 Application

修改内容如下：

重复上面创建包的操作，把需要的包都建好，如下图：

4、使用 Mybatis Generator 自动生成实体类、mapper和mapper.xml文件

请参考文章链接：https://blog.csdn.net/qq_39688441/article/details/123851515

5、填写各个包的内容

由于生成的一套，除了基本的，其他没有，实际使用还得自己来根据实际情况编写

①mapper 增加一个方法

mapper 里就是数据库操作的方法

这里简单，只要定好返回值类型、方法名和参数就OK啦

②mapper.xml 的写法

如上图，1 为编写的返回值类型，即为，这个返回值要返回哪些字段

2 为引用的返回值的id

如上图，可以把常用的一段sql 提出来，

在需要用到的地方 include 进去

如上图为具体的拼写sql

③service 层接口的编写

这层也很好写，想好要干的事，定好服务名、返回参数和入参

④service 的 Impl 实现类

注意 class 类前面要 @Service 声明这是业务层组件

这里就是写业务逻辑，一个业务要干什么，一个业务也会调多个数据库操作，我这里就简单调用一个查询

⑤Controller 层

到这里，基本上就写完了

五、运行

运行步骤如下

打开 Application.Java 文件，文件中点击反键，Run As... → Java Application

启动成功后：

http://localhost:8080/boot/getUserByNickname

http://localhost:8080/boot/getUserByNickname?name=lz

实际上刚建好时一运行就报错，具体状况请看下面六、2、3、4、5、

六、遇到的问题以及解决方案

1、刚建好项目，啥都没干呢就看到 index.jsp 红叉，如下：

错误状况：

刚建完maven项目，一看红X，赶紧进去看了下

打开index.jsp后，如下问题

解决方案：

反键 Build Path 里

Jave Build Path 里选择如下图红框

选择合适的tomcat

应用并关闭，很快就运行好了

报错已经解决

2、项目基本写完，没看到红叉之类的错误提示，但是一运行，报错

错误状况：

具体报错如下，我贴出来：

14:36:01.267 [main] DEBUG org.springframework.boot.context.logging.ClasspathLoggingApplicationListener - Application failed to start with classpath: [file:/D:/jdk1.8.0_101/jre/lib/resources.jar, file:/D:/jdk1.8.0_101/jre/lib/rt.jar, file:/D:/jdk1.8.0_101/jre/lib/jsse.jar, file:/D:/jdk1.8.0_101/jre/lib/jce.jar, file:/D:/jdk1.8.0_101/jre/lib/charsets.jar, file:/D:/jdk1.8.0_101/jre/lib/jfr.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/access-bridge-64.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/cldrdata.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/dnsns.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/jaccess.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/jfxrt.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/localedata.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/nashorn.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/sunec.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/sunjce_provider.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/sunmscapi.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/sunpkcs11.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/zipfs.jar, file:/D:/Work/springboot_demo/target/classes/, file:/D:/tomcat/apache-tomcat-9.0.60/lib/annotations-api.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/catalina-ant.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/catalina-ha.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/catalina-ssi.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/catalina-storeconfig.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/catalina-tribes.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/catalina.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/ecj-4.20.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/el-api.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/jasper-el.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/jasper.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/jaspic-api.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/jsp-api.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/servlet-api.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-api.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-coyote.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-dbcp.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-cs.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-de.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-es.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-fr.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-ja.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-ko.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-pt-BR.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-ru.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-zh-CN.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-jdbc.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-jni.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-util-scan.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-util.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-websocket.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/websocket-api.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-web/2.3.1.RELEASE/spring-boot-starter-web-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter/2.3.1.RELEASE/spring-boot-starter-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot/2.3.1.RELEASE/spring-boot-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-autoconfigure/2.3.1.RELEASE/spring-boot-autoconfigure-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-logging/2.3.1.RELEASE/spring-boot-starter-logging-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar, file:/C:/Users/397004497/.m2/repository/ch/qos/logback/logback-core/1.2.3/logback-core-1.2.3.jar, file:/C:/Users/397004497/.m2/repository/org/apache/logging/log4j/log4j-to-slf4j/2.13.3/log4j-to-slf4j-2.13.3.jar, file:/C:/Users/397004497/.m2/repository/org/apache/logging/log4j/log4j-api/2.13.3/log4j-api-2.13.3.jar, file:/C:/Users/397004497/.m2/repository/org/slf4j/jul-to-slf4j/1.7.30/jul-to-slf4j-1.7.30.jar, file:/C:/Users/397004497/.m2/repository/jakarta/annotation/jakarta.annotation-api/1.3.5/jakarta.annotation-api-1.3.5.jar, file:/C:/Users/397004497/.m2/repository/org/yaml/snakeyaml/1.26/snakeyaml-1.26.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-json/2.3.1.RELEASE/spring-boot-starter-json-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/jackson/core/jackson-databind/2.11.0/jackson-databind-2.11.0.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/jackson/core/jackson-annotations/2.11.0/jackson-annotations-2.11.0.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/jackson/core/jackson-core/2.11.0/jackson-core-2.11.0.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jdk8/2.11.0/jackson-datatype-jdk8-2.11.0.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jsr310/2.11.0/jackson-datatype-jsr310-2.11.0.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/jackson/module/jackson-module-parameter-names/2.11.0/jackson-module-parameter-names-2.11.0.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-tomcat/2.3.1.RELEASE/spring-boot-starter-tomcat-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/apache/tomcat/embed/tomcat-embed-core/9.0.36/tomcat-embed-core-9.0.36.jar, file:/C:/Users/397004497/.m2/repository/org/glassfish/jakarta.el/3.0.3/jakarta.el-3.0.3.jar, file:/C:/Users/397004497/.m2/repository/org/apache/tomcat/embed/tomcat-embed-websocket/9.0.36/tomcat-embed-websocket-9.0.36.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-web/5.2.7.RELEASE/spring-web-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-beans/5.2.7.RELEASE/spring-beans-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-webmvc/5.2.7.RELEASE/spring-webmvc-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-context/5.2.7.RELEASE/spring-context-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-expression/5.2.7.RELEASE/spring-expression-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-data-jpa/2.3.1.RELEASE/spring-boot-starter-data-jpa-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-jdbc/2.3.1.RELEASE/spring-boot-starter-jdbc-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/com/zaxxer/HikariCP/3.4.5/HikariCP-3.4.5.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-jdbc/5.2.7.RELEASE/spring-jdbc-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/jakarta/transaction/jakarta.transaction-api/1.3.3/jakarta.transaction-api-1.3.3.jar, file:/C:/Users/397004497/.m2/repository/jakarta/persistence/jakarta.persistence-api/2.2.3/jakarta.persistence-api-2.2.3.jar, file:/C:/Users/397004497/.m2/repository/org/hibernate/hibernate-core/5.4.17.Final/hibernate-core-5.4.17.Final.jar, file:/C:/Users/397004497/.m2/repository/org/jboss/logging/jboss-logging/3.4.1.Final/jboss-logging-3.4.1.Final.jar, file:/C:/Users/397004497/.m2/repository/org/javassist/javassist/3.24.0-GA/javassist-3.24.0-GA.jar, file:/C:/Users/397004497/.m2/repository/net/bytebuddy/byte-buddy/1.10.11/byte-buddy-1.10.11.jar, file:/C:/Users/397004497/.m2/repository/antlr/antlr/2.7.7/antlr-2.7.7.jar, file:/C:/Users/397004497/.m2/repository/org/jboss/jandex/2.1.3.Final/jandex-2.1.3.Final.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/classmate/1.5.1/classmate-1.5.1.jar, file:/C:/Users/397004497/.m2/repository/org/dom4j/dom4j/2.1.3/dom4j-2.1.3.jar, file:/C:/Users/397004497/.m2/repository/org/hibernate/common/hibernate-commons-annotations/5.1.0.Final/hibernate-commons-annotations-5.1.0.Final.jar, file:/C:/Users/397004497/.m2/repository/org/glassfish/jaxb/jaxb-runtime/2.3.3/jaxb-runtime-2.3.3.jar, file:/C:/Users/397004497/.m2/repository/org/glassfish/jaxb/txw2/2.3.3/txw2-2.3.3.jar, file:/C:/Users/397004497/.m2/repository/com/sun/istack/istack-commons-runtime/3.0.11/istack-commons-runtime-3.0.11.jar, file:/C:/Users/397004497/.m2/repository/com/sun/activation/jakarta.activation/1.2.2/jakarta.activation-1.2.2.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/data/spring-data-jpa/2.3.1.RELEASE/spring-data-jpa-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/data/spring-data-commons/2.3.1.RELEASE/spring-data-commons-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-orm/5.2.7.RELEASE/spring-orm-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-tx/5.2.7.RELEASE/spring-tx-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/slf4j/slf4j-api/1.7.30/slf4j-api-1.7.30.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-aspects/5.2.7.RELEASE/spring-aspects-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/mysql/mysql-connector-java/8.0.20/mysql-connector-java-8.0.20.jar, file:/C:/Users/397004497/.m2/repository/org/mybatis/spring/boot/mybatis-spring-boot-starter/2.1.3/mybatis-spring-boot-starter-2.1.3.jar, file:/C:/Users/397004497/.m2/repository/org/mybatis/spring/boot/mybatis-spring-boot-autoconfigure/2.1.3/mybatis-spring-boot-autoconfigure-2.1.3.jar, file:/C:/Users/397004497/.m2/repository/org/mybatis/mybatis/3.5.5/mybatis-3.5.5.jar, file:/C:/Users/397004497/.m2/repository/org/mybatis/mybatis-spring/2.0.5/mybatis-spring-2.0.5.jar, file:/C:/Users/397004497/.m2/repository/jakarta/xml/bind/jakarta.xml.bind-api/2.3.3/jakarta.xml.bind-api-2.3.3.jar, file:/C:/Users/397004497/.m2/repository/jakarta/activation/jakarta.activation-api/1.2.2/jakarta.activation-api-1.2.2.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-core/5.2.7.RELEASE/spring-core-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-jcl/5.2.7.RELEASE/spring-jcl-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/com/alibaba/druid-spring-boot-starter/1.2.6/druid-spring-boot-starter-1.2.6.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-aop/2.3.1.RELEASE/spring-boot-starter-aop-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-aop/5.2.7.RELEASE/spring-aop-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/aspectj/aspectjweaver/1.9.5/aspectjweaver-1.9.5.jar, file:/C:/Users/397004497/.m2/repository/org/mybatis/generator/mybatis-generator-core/1.3.5/mybatis-generator-core-1.3.5.jar]
14:36:01.355 [main] ERROR org.springframework.boot.SpringApplication - Application run failed
java.lang.IllegalStateException: Failed to load property source from 'file:/D:/Work/springboot_demo/target/classes/application.yml' (classpath:/application.yml)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:554)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.loadForFileExtension(ConfigFileApplicationListener.java:499)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:469)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.lambda$null$7(ConfigFileApplicationListener.java:448)at java.lang.Iterable.forEach(Iterable.java:75)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.lambda$load$8(ConfigFileApplicationListener.java:448)at java.lang.Iterable.forEach(Iterable.java:75)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:445)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.lambda$load$0(ConfigFileApplicationListener.java:348)at org.springframework.boot.context.config.FilteredPropertySource.apply(FilteredPropertySource.java:54)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:336)at org.springframework.boot.context.config.ConfigFileApplicationListener.addPropertySources(ConfigFileApplicationListener.java:226)at org.springframework.boot.context.config.ConfigFileApplicationListener.postProcessEnvironment(ConfigFileApplicationListener.java:210)at org.springframework.boot.context.config.ConfigFileApplicationListener.onApplicationEnvironmentPreparedEvent(ConfigFileApplicationListener.java:200)at org.springframework.boot.context.config.ConfigFileApplicationListener.onApplicationEvent(ConfigFileApplicationListener.java:188)at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:127)at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:80)at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:53)at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:345)at org.springframework.boot.SpringApplication.run(SpringApplication.java:308)at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237)at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226)at com.lx.springboot_demo.Application.main(Application.java:19)
Caused by: org.yaml.snakeyaml.scanner.ScannerException: while scanning for the next token
found character '\t(TAB)' that cannot start any token. (Do not use \t(TAB) for indentation)in 'reader', line 6, column 3:#驱动^at org.yaml.snakeyaml.scanner.ScannerImpl.fetchMoreTokens(ScannerImpl.java:419)at org.yaml.snakeyaml.scanner.ScannerImpl.checkToken(ScannerImpl.java:227)at org.yaml.snakeyaml.parser.ParserImpl$ParseBlockMappingValue.produce(ParserImpl.java:586)at org.yaml.snakeyaml.parser.ParserImpl.peekEvent(ParserImpl.java:158)at org.yaml.snakeyaml.parser.ParserImpl.checkEvent(ParserImpl.java:148)at org.yaml.snakeyaml.composer.Composer.composeNode(Composer.java:136)at org.yaml.snakeyaml.composer.Composer.composeValueNode(Composer.java:257)at org.yaml.snakeyaml.composer.Composer.composeMappingChildren(Composer.java:248)at org.yaml.snakeyaml.composer.Composer.composeMappingNode(Composer.java:236)at org.yaml.snakeyaml.composer.Composer.composeNode(Composer.java:162)at org.yaml.snakeyaml.composer.Composer.composeValueNode(Composer.java:257)at org.yaml.snakeyaml.composer.Composer.composeMappingChildren(Composer.java:248)at org.yaml.snakeyaml.composer.Composer.composeMappingNode(Composer.java:236)at org.yaml.snakeyaml.composer.Composer.composeNode(Composer.java:162)at org.yaml.snakeyaml.composer.Composer.getNode(Composer.java:95)at org.yaml.snakeyaml.constructor.BaseConstructor.getData(BaseConstructor.java:134)at org.yaml.snakeyaml.Yaml$1.next(Yaml.java:494)at org.springframework.beans.factory.config.YamlProcessor.process(YamlProcessor.java:200)at org.springframework.beans.factory.config.YamlProcessor.process(YamlProcessor.java:164)at org.springframework.boot.env.OriginTrackedYamlLoader.load(OriginTrackedYamlLoader.java:76)at org.springframework.boot.env.YamlPropertySourceLoader.load(YamlPropertySourceLoader.java:50)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.loadDocuments(ConfigFileApplicationListener.java:608)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:524)... 25 common frames omitted

小小分析：

首先找到最开始报错的地方，

java.lang.IllegalStateException: Failed to load property source from 'file:/D:/Work/springboot_demo/target/classes/application.yml' (classpath:/application.yml)

Failed to load property source from ‘file:/xxxxxxxxxxxxxx.xxxxx.yml’ (classpath:/application.yml)

这个是说你的yml有问题，可能是语法有错

咋们往下翻：

这就是提示了

打开 yml 文件

看到了吗，和上面提示的一样，第6行，第3个位置开始的 “#驱动”

我这里，一看，这个中文注释是这个文件的第一个中文注释

所以我猜是注释有问题

解决方案：

把 yml 文件里所有注释全部删掉

3、再次运行，又报错了，

错误状况：

2022-04-02 16:03:36.377 ERROR 24484 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : 在路径为的上下文中，Servlet[dispatcherServlet]的Servlet.service（）引发了具有根本原因的异常Request processing failed; nested exception is java.lang.NullPointerExceptionjava.lang.NullPointerException: nullat com.lx.springboot_demo.controller.UserMainController.getUserByNickname(UserMainController.java:22) ~[classes/:na]at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_101]at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_101]at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_101]at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_101]at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]

查找问题：

通过打印语句，发现， Controller 层已经进入，没进 Service 层，

检查注解，发现 Controller 层用 Service 时，忘了注入了

加上自动注入

进入到service层打印，但是又报错

2022-04-02 16:08:46.374 ERROR 23972 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : 在路径为的上下文中，Servlet[dispatcherServlet]的Servlet.service（）引发了具有根本原因的异常Request processing failed; nested exception is java.lang.IllegalArgumentException: Result Maps collection does not contain value for com.lx.springboot_demo.dao.UserMainMapper.Listjava.lang.IllegalArgumentException: Result Maps collection does not contain value for com.lx.springboot_demo.dao.UserMainMapper.Listat org.apache.ibatis.session.Configuration$StrictMap.get(Configuration.java:1009) ~[mybatis-3.5.5.jar:3.5.5]at org.apache.ibatis.session.Configuration.getResultMap(Configuration.java:718) ~[mybatis-3.5.5.jar:3.5.5]at org.apache.ibatis.builder.MapperBuilderAssistant.getStatementResultMaps(MapperBuilderAssistant.java:394) ~[mybatis-3.5.5.jar:3.5.5]at org.apache.ibatis.builder.MapperBuilderAssistant.addMappedStatement(MapperBuilderAssistant.java:285) ~[mybatis-3.5.5.jar:3.5.5]

定位到问题发生位置后，百度解决：

百度后说是

如上图，确实用错了

修改如下图，也是不对的。

我要查的是多条实体。最后改为下图这样就好了。

前面是我想错了，这里 resultMap 是返回结果的每一个实体的的类型，而不是返回结果的类型

4、Application run failed 启动失败

错误状况：

09:50:14.499 [main] DEBUG org.springframework.boot.context.logging.ClasspathLoggingApplicationListener - Application failed to start with classpath: [file:/D:/jdk1.8.0_101/jre/lib/resources.jar, file:/D:/jdk1.8.0_101/jre/lib/rt.jar, file:/D:/jdk1.8.0_101/jre/lib/jsse.jar, file:/D:/jdk1.8.0_101/jre/lib/jce.jar, file:/D:/jdk1.8.0_101/jre/lib/charsets.jar, file:/D:/jdk1.8.0_101/jre/lib/jfr.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/access-bridge-64.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/cldrdata.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/dnsns.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/jaccess.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/jfxrt.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/localedata.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/nashorn.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/sunec.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/sunjce_provider.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/sunmscapi.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/sunpkcs11.jar, file:/D:/jdk1.8.0_101/jre/lib/ext/zipfs.jar, file:/D:/Work/springboot_demo/target/classes/, file:/D:/tomcat/apache-tomcat-9.0.60/lib/annotations-api.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/catalina-ant.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/catalina-ha.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/catalina-ssi.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/catalina-storeconfig.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/catalina-tribes.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/catalina.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/ecj-4.20.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/el-api.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/jasper-el.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/jasper.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/jaspic-api.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/jsp-api.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/servlet-api.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-api.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-coyote.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-dbcp.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-cs.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-de.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-es.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-fr.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-ja.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-ko.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-pt-BR.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-ru.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-i18n-zh-CN.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-jdbc.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-jni.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-util-scan.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-util.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/tomcat-websocket.jar, file:/D:/tomcat/apache-tomcat-9.0.60/lib/websocket-api.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-web/2.3.1.RELEASE/spring-boot-starter-web-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter/2.3.1.RELEASE/spring-boot-starter-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot/2.3.1.RELEASE/spring-boot-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-autoconfigure/2.3.1.RELEASE/spring-boot-autoconfigure-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-logging/2.3.1.RELEASE/spring-boot-starter-logging-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar, file:/C:/Users/397004497/.m2/repository/ch/qos/logback/logback-core/1.2.3/logback-core-1.2.3.jar, file:/C:/Users/397004497/.m2/repository/org/apache/logging/log4j/log4j-to-slf4j/2.13.3/log4j-to-slf4j-2.13.3.jar, file:/C:/Users/397004497/.m2/repository/org/apache/logging/log4j/log4j-api/2.13.3/log4j-api-2.13.3.jar, file:/C:/Users/397004497/.m2/repository/org/slf4j/jul-to-slf4j/1.7.30/jul-to-slf4j-1.7.30.jar, file:/C:/Users/397004497/.m2/repository/jakarta/annotation/jakarta.annotation-api/1.3.5/jakarta.annotation-api-1.3.5.jar, file:/C:/Users/397004497/.m2/repository/org/yaml/snakeyaml/1.26/snakeyaml-1.26.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-json/2.3.1.RELEASE/spring-boot-starter-json-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/jackson/core/jackson-databind/2.11.0/jackson-databind-2.11.0.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/jackson/core/jackson-annotations/2.11.0/jackson-annotations-2.11.0.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/jackson/core/jackson-core/2.11.0/jackson-core-2.11.0.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jdk8/2.11.0/jackson-datatype-jdk8-2.11.0.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jsr310/2.11.0/jackson-datatype-jsr310-2.11.0.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/jackson/module/jackson-module-parameter-names/2.11.0/jackson-module-parameter-names-2.11.0.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-tomcat/2.3.1.RELEASE/spring-boot-starter-tomcat-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/apache/tomcat/embed/tomcat-embed-core/9.0.36/tomcat-embed-core-9.0.36.jar, file:/C:/Users/397004497/.m2/repository/org/glassfish/jakarta.el/3.0.3/jakarta.el-3.0.3.jar, file:/C:/Users/397004497/.m2/repository/org/apache/tomcat/embed/tomcat-embed-websocket/9.0.36/tomcat-embed-websocket-9.0.36.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-web/5.2.7.RELEASE/spring-web-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-beans/5.2.7.RELEASE/spring-beans-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-webmvc/5.2.7.RELEASE/spring-webmvc-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-context/5.2.7.RELEASE/spring-context-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-expression/5.2.7.RELEASE/spring-expression-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-data-jpa/2.3.1.RELEASE/spring-boot-starter-data-jpa-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-jdbc/2.3.1.RELEASE/spring-boot-starter-jdbc-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/com/zaxxer/HikariCP/3.4.5/HikariCP-3.4.5.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-jdbc/5.2.7.RELEASE/spring-jdbc-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/jakarta/transaction/jakarta.transaction-api/1.3.3/jakarta.transaction-api-1.3.3.jar, file:/C:/Users/397004497/.m2/repository/jakarta/persistence/jakarta.persistence-api/2.2.3/jakarta.persistence-api-2.2.3.jar, file:/C:/Users/397004497/.m2/repository/org/hibernate/hibernate-core/5.4.17.Final/hibernate-core-5.4.17.Final.jar, file:/C:/Users/397004497/.m2/repository/org/jboss/logging/jboss-logging/3.4.1.Final/jboss-logging-3.4.1.Final.jar, file:/C:/Users/397004497/.m2/repository/org/javassist/javassist/3.24.0-GA/javassist-3.24.0-GA.jar, file:/C:/Users/397004497/.m2/repository/net/bytebuddy/byte-buddy/1.10.11/byte-buddy-1.10.11.jar, file:/C:/Users/397004497/.m2/repository/antlr/antlr/2.7.7/antlr-2.7.7.jar, file:/C:/Users/397004497/.m2/repository/org/jboss/jandex/2.1.3.Final/jandex-2.1.3.Final.jar, file:/C:/Users/397004497/.m2/repository/com/fasterxml/classmate/1.5.1/classmate-1.5.1.jar, file:/C:/Users/397004497/.m2/repository/org/dom4j/dom4j/2.1.3/dom4j-2.1.3.jar, file:/C:/Users/397004497/.m2/repository/org/hibernate/common/hibernate-commons-annotations/5.1.0.Final/hibernate-commons-annotations-5.1.0.Final.jar, file:/C:/Users/397004497/.m2/repository/org/glassfish/jaxb/jaxb-runtime/2.3.3/jaxb-runtime-2.3.3.jar, file:/C:/Users/397004497/.m2/repository/org/glassfish/jaxb/txw2/2.3.3/txw2-2.3.3.jar, file:/C:/Users/397004497/.m2/repository/com/sun/istack/istack-commons-runtime/3.0.11/istack-commons-runtime-3.0.11.jar, file:/C:/Users/397004497/.m2/repository/com/sun/activation/jakarta.activation/1.2.2/jakarta.activation-1.2.2.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/data/spring-data-jpa/2.3.1.RELEASE/spring-data-jpa-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/data/spring-data-commons/2.3.1.RELEASE/spring-data-commons-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-orm/5.2.7.RELEASE/spring-orm-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-tx/5.2.7.RELEASE/spring-tx-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/slf4j/slf4j-api/1.7.30/slf4j-api-1.7.30.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-aspects/5.2.7.RELEASE/spring-aspects-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/mysql/mysql-connector-java/8.0.20/mysql-connector-java-8.0.20.jar, file:/C:/Users/397004497/.m2/repository/org/mybatis/spring/boot/mybatis-spring-boot-starter/2.1.3/mybatis-spring-boot-starter-2.1.3.jar, file:/C:/Users/397004497/.m2/repository/org/mybatis/spring/boot/mybatis-spring-boot-autoconfigure/2.1.3/mybatis-spring-boot-autoconfigure-2.1.3.jar, file:/C:/Users/397004497/.m2/repository/org/mybatis/mybatis/3.5.5/mybatis-3.5.5.jar, file:/C:/Users/397004497/.m2/repository/org/mybatis/mybatis-spring/2.0.5/mybatis-spring-2.0.5.jar, file:/C:/Users/397004497/.m2/repository/jakarta/xml/bind/jakarta.xml.bind-api/2.3.3/jakarta.xml.bind-api-2.3.3.jar, file:/C:/Users/397004497/.m2/repository/jakarta/activation/jakarta.activation-api/1.2.2/jakarta.activation-api-1.2.2.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-core/5.2.7.RELEASE/spring-core-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-jcl/5.2.7.RELEASE/spring-jcl-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/com/alibaba/druid-spring-boot-starter/1.2.6/druid-spring-boot-starter-1.2.6.jar, file:/C:/Users/397004497/.m2/repository/com/alibaba/druid/1.2.6/druid-1.2.6.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/boot/spring-boot-starter-aop/2.3.1.RELEASE/spring-boot-starter-aop-2.3.1.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/springframework/spring-aop/5.2.7.RELEASE/spring-aop-5.2.7.RELEASE.jar, file:/C:/Users/397004497/.m2/repository/org/aspectj/aspectjweaver/1.9.5/aspectjweaver-1.9.5.jar, file:/C:/Users/397004497/.m2/repository/org/mybatis/generator/mybatis-generator-core/1.3.5/mybatis-generator-core-1.3.5.jar]
09:50:14.848 [main] ERROR org.springframework.boot.SpringApplication - Application run failed
java.lang.IllegalStateException: Failed to load property source from 'file:/D:/Work/springboot_demo/target/classes/application.yml' (classpath:/application.yml)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:554)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.loadForFileExtension(ConfigFileApplicationListener.java:499)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:469)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.lambda$null$7(ConfigFileApplicationListener.java:448)at java.lang.Iterable.forEach(Iterable.java:75)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.lambda$load$8(ConfigFileApplicationListener.java:448)at java.lang.Iterable.forEach(Iterable.java:75)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:445)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.lambda$load$0(ConfigFileApplicationListener.java:348)at org.springframework.boot.context.config.FilteredPropertySource.apply(FilteredPropertySource.java:54)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:336)at org.springframework.boot.context.config.ConfigFileApplicationListener.addPropertySources(ConfigFileApplicationListener.java:226)at org.springframework.boot.context.config.ConfigFileApplicationListener.postProcessEnvironment(ConfigFileApplicationListener.java:210)at org.springframework.boot.context.config.ConfigFileApplicationListener.onApplicationEnvironmentPreparedEvent(ConfigFileApplicationListener.java:200)at org.springframework.boot.context.config.ConfigFileApplicationListener.onApplicationEvent(ConfigFileApplicationListener.java:188)at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:127)at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:80)at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:53)at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:345)at org.springframework.boot.SpringApplication.run(SpringApplication.java:308)at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237)at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226)at com.lx.springboot_demo.Application.main(Application.java:19)
Caused by: org.yaml.snakeyaml.scanner.ScannerException: while scanning for the next token
found character '\t(TAB)' that cannot start any token. (Do not use \t(TAB) for indentation)in 'reader', line 39, column 1:mapper-locations: class:mappers ... ^at org.yaml.snakeyaml.scanner.ScannerImpl.fetchMoreTokens(ScannerImpl.java:419)at org.yaml.snakeyaml.scanner.ScannerImpl.checkToken(ScannerImpl.java:227)at org.yaml.snakeyaml.parser.ParserImpl$ParseBlockMappingValue.produce(ParserImpl.java:586)at org.yaml.snakeyaml.parser.ParserImpl.peekEvent(ParserImpl.java:158)at org.yaml.snakeyaml.parser.ParserImpl.checkEvent(ParserImpl.java:148)at org.yaml.snakeyaml.composer.Composer.composeNode(Composer.java:136)at org.yaml.snakeyaml.composer.Composer.composeValueNode(Composer.java:257)at org.yaml.snakeyaml.composer.Composer.composeMappingChildren(Composer.java:248)at org.yaml.snakeyaml.composer.Composer.composeMappingNode(Composer.java:236)at org.yaml.snakeyaml.composer.Composer.composeNode(Composer.java:162)at org.yaml.snakeyaml.composer.Composer.getNode(Composer.java:95)at org.yaml.snakeyaml.constructor.BaseConstructor.getData(BaseConstructor.java:134)at org.yaml.snakeyaml.Yaml$1.next(Yaml.java:494)at org.springframework.beans.factory.config.YamlProcessor.process(YamlProcessor.java:200)at org.springframework.beans.factory.config.YamlProcessor.process(YamlProcessor.java:164)at org.springframework.boot.env.OriginTrackedYamlLoader.load(OriginTrackedYamlLoader.java:76)at org.springframework.boot.env.YamlPropertySourceLoader.load(YamlPropertySourceLoader.java:50)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.loadDocuments(ConfigFileApplicationListener.java:608)at org.springframework.boot.context.config.ConfigFileApplicationListener$Loader.load(ConfigFileApplicationListener.java:524)... 25 common frames omitted

java.lang.IllegalStateException: Failed to load property source from 'file:/D:/Work/springboot_demo/target/classes/application.yml' (classpath:/application.yml)

如上图，它总是提示我，这块有问题，可是我检查，yml配置文件，看起来没写错

小小分析：

注意看这里

这个算是小箭头吧，它标注的位置，在我代码前面的空白

我没明白，不过我各种实验过，反正只要把 mybatis：这些东西全删除，居然能正常启动，并且正常调用返回。那我确定就是mybatis这块写错了。

解决方案：

最终，实验到我把前面空白去掉，他就不报这一行错误。

然后和上面复制粘贴过来的进行对比，发现，这几行报错的前面我按得是 “Tab” 按键，而正确的代码里，前面的空白用的是多个空格键

修改后，如下：

mybatis:mapper-locations: class:mappers/*.xmltype-aliases-package: com.lx.springboot_demo.modelconfiguration:map-underscore-to-camel-case: true

把前面缩进的位置都用空格键来缩进

启动，问题解决。

5、启动已经没问题，但是控制台有一个警告

警告详情：

启动时，控制台如下：

.   ____          _            __ _ _/\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \\\/  ___)| |_)| | | | | || (_| |  ) ) ) )'  |____| .__|_| |_|_| |_\__, | / / / /=========|_|==============|___/=/_/_/_/:: Spring Boot ::        (v2.3.1.RELEASE)2022-04-06 10:04:00.230  INFO 28028 --- [           main] com.lx.springboot_demo.Application       : Starting Application on LAPTOP-710QH23H with PID 28028 (D:\Work\springboot_demo\target\classes started by 397004497 in D:\Work\springboot_demo)
2022-04-06 10:04:00.233  INFO 28028 --- [           main] com.lx.springboot_demo.Application       : No active profile set, falling back to default profiles: default
2022-04-06 10:04:01.983  INFO 28028 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JPA repositories in DEFERRED mode.
2022-04-06 10:04:02.015  INFO 28028 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 20ms. Found 0 JPA repository interfaces.
2022-04-06 10:04:04.386  INFO 28028 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2022-04-06 10:04:04.453  INFO 28028 --- [           main] o.apache.catalina.core.StandardService   : 正在启动服务[Tomcat]
2022-04-06 10:04:04.453  INFO 28028 --- [           main] org.apache.catalina.core.StandardEngine  : 正在启动 Servlet 引擎：[Apache Tomcat/9.0.60]
2022-04-06 10:04:04.454  WARN 28028 --- [           main] o.a.catalina.core.AprLifecycleListener   : This listener must only be nested within Server elements, but is in [TomcatEmbeddedContext].
2022-04-06 10:04:04.455  INFO 28028 --- [           main] o.a.catalina.core.AprLifecycleListener   : 使用APR版本[1.7.0]加载了基于APR的Apache Tomcat本机库[1.2.31]。
2022-04-06 10:04:04.455  INFO 28028 --- [           main] o.a.catalina.core.AprLifecycleListener   : APR功能：IPv6[true]、sendfile[true]、accept filters[false]、random[true]、UDS [true]。
2022-04-06 10:04:04.455  INFO 28028 --- [           main] o.a.catalina.core.AprLifecycleListener   : APR/OpenSSL配置：useAprConnector[false]，useOpenSSL[true]
2022-04-06 10:04:04.635  INFO 28028 --- [           main] o.a.catalina.core.AprLifecycleListener   : OpenSSL成功初始化 [OpenSSL 1.1.1l  24 Aug 2021]
2022-04-06 10:04:05.643  INFO 28028 --- [           main] org.apache.jasper.servlet.TldScanner     : 至少有一个JAR被扫描用于TLD但尚未包含TLD。 为此记录器启用调试日志记录，以获取已扫描但未在其中找到TLD的完整JAR列表。 在扫描期间跳过不需要的JAR可以缩短启动时间和JSP编译时间。
2022-04-06 10:04:05.647  INFO 28028 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2022-04-06 10:04:05.648  INFO 28028 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 5329 ms
2022-04-06 10:04:05.926  INFO 28028 --- [           main] c.a.d.s.b.a.DruidDataSourceAutoConfigure : Init DruidDataSource
Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.
2022-04-06 10:04:10.829  INFO 28028 --- [           main] com.alibaba.druid.pool.DruidDataSource   : {dataSource-1} inited
2022-04-06 10:04:11.091  INFO 28028 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2022-04-06 10:04:11.285  INFO 28028 --- [         task-1] o.hibernate.jpa.internal.util.LogHelper  : HHH000204: Processing PersistenceUnitInfo [name: default]
2022-04-06 10:04:11.488  INFO 28028 --- [         task-1] org.hibernate.Version                    : HHH000412: Hibernate ORM core version 5.4.17.Final
2022-04-06 10:04:12.192  WARN 28028 --- [           main] JpaBaseConfiguration$JpaWebConfiguration : spring.jpa.open-in-view is enabled by default. Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning
2022-04-06 10:04:12.277  INFO 28028 --- [         task-1] o.hibernate.annotations.common.Version   : HCANN000001: Hibernate Commons Annotations {5.1.0.Final}
2022-04-06 10:04:12.948  INFO 28028 --- [         task-1] org.hibernate.dialect.Dialect            : HHH000400: Using dialect: org.hibernate.dialect.MySQL57Dialect
2022-04-06 10:04:13.545  INFO 28028 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2022-04-06 10:04:13.546  INFO 28028 --- [           main] DeferredRepositoryInitializationListener : Triggering deferred initialization of Spring Data repositories…
2022-04-06 10:04:13.547  INFO 28028 --- [           main] DeferredRepositoryInitializationListener : Spring Data repositories initialized!
2022-04-06 10:04:13.567  INFO 28028 --- [           main] com.lx.springboot_demo.Application       : Started Application in 14.39 seconds (JVM running for 14.968)
2022-04-06 10:04:13.824  INFO 28028 --- [         task-1] o.h.e.t.j.p.i.JtaPlatformInitiator       : HHH000490: Using JtaPlatform implementation: [org.hibernate.engine.transaction.jta.platform.internal.NoJtaPlatform]
2022-04-06 10:04:13.839  INFO 28028 --- [         task-1] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default'

出现了

一行红字，百度翻译了下

正在加载class`com。mysql。jdbc。司机。这是不赞成的。新的驱动程序类是'com。mysql。希杰。jdbc。司机。驱动程序通过SPI自动注册，通常不需要手动加载驱动程序类。

意思是：不赞成加载 “com.mysql.jdbc.Driver” 驱动。新的驱动程序类 “com.mysql.cj.jdbc.Driver”。自动注册，不需要手动加载

问题所在：

配置文件加载驱动应该改了

解决问题：

修改驱动类名

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Eclipse 工具上Springboot项目的简单增删改查的搭建

一、为嘛子要学习Springboot

二、简单的说下springboot

三、咱们对比看看呗

四、开始操作，建项目

1、建一个maven项目

2、pom.xml 依赖以及配置文件

①简单的依赖如下，我就不细说了

②配置文件，application.yml

3、创建相应的包结构

4、使用 Mybatis Generator 自动生成实体类、mapper和mapper.xml文件

5、填写各个包的内容

①mapper 增加一个方法

②mapper.xml 的写法

③service 层接口的编写

④service 的 Impl 实现类

⑤Controller 层

五、运行

六、遇到的问题以及解决方案

1、刚建好项目，啥都没干呢就看到 index.jsp 红叉，如下：

错误状况：

解决方案：

2、项目基本写完，没看到红叉之类的错误提示，但是一运行，报错

错误状况：

小小分析：

解决方案：

3、再次运行，又报错了，

错误状况：

查找问题：

定位到问题发生位置后，百度解决：

4、Application run failed 启动失败

小小分析：

解决方案：

5、启动已经没问题，但是控制台有一个警告

警告详情：

问题所在：

解决问题：

Eclipse 工具上Springboot项目的简单增删改查的搭建相关推荐

最新文章

热门文章

Eclipse 工具上Springboot项目的简单 增删改查 的搭建

一、为嘛子要学习Springboot

二、简单的说下springboot

三、咱们对比看看呗

四、开始操作，建项目

1、建一个maven项目

2、pom.xml 依赖 以及 配置文件

①简单的依赖如下，我就不细说了

②配置文件，application.yml

3、创建相应的包结构

4、使用 Mybatis Generator 自动生成实体类、mapper和mapper.xml文件

5、填写各个包的内容

①mapper 增加一个方法

②mapper.xml 的写法

③service 层接口的编写

④service 的 Impl 实现类

⑤Controller 层

五、运行

六、遇到的问题以及解决方案

1、刚建好项目，啥都没干呢就看到 index.jsp 红叉，如下：

错误状况：

解决方案：

2、项目基本写完，没看到红叉之类的错误提示，但是一运行，报错

错误状况：

小小分析：

解决方案：

3、再次运行，又报错了，

错误状况：

查找问题：

定位到问题发生位置后，百度解决：

4、Application run failed 启动失败

小小分析：

解决方案：

5、启动已经没问题，但是控制台有一个警告

警告详情：

问题所在：

解决问题：

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