Spring Boot有两种方法与数据库建立连接，一种是使用JdbcTemplate，另一种集成Mybatis，下面分别为大家介绍一下如何集成和使用这两种方式。

1. 使用JdbcTemplate

<dependency>    <groupId>mysql</groupId>    <artifactId>mysql-connector-java</artifactId></dependency><dependency>    <groupId>org.springframework.boot</groupId>    <artifactId>spring-boot-starter-jdbc</artifactId></dependency>

在resource文件夹下添加application.properties配置文件并输入数据库参数，内容如下：

spring.datasource.url=jdbc:mysql://127.0.0.1:3306/testspring.datasource.username=rootspring.datasource.password=123456spring.datasource.driver-class-name=com.mysql.jdbc.Driverspring.datasource.max-idle=10spring.datasource.max-wait=1000spring.datasource.min-idle=5spring.datasource.initial-size=5server.port=8012server.session.timeout=10server.tomcat.uri-encoding=UTF-8

新建Controller类测试数据库连接，实例如下：

package com.example.demo;import java.util.Iterator;import java.util.List;import java.util.Map;import java.util.Map.Entry;import java.util.Set;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.jdbc.core.JdbcTemplate;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;@RestController@RequestMapping("/mydb")public class DBController {    @Autowired    private JdbcTemplate jdbcTemplate;

    @RequestMapping("/getUsers")    public List<Map<String, Object>> getDbType(){        String sql = "select * from appuser";        List<Map<String, Object>> list =  jdbcTemplate.queryForList(sql);        for (Map<String, Object> map : list) {            Set<Entry<String, Object>> entries = map.entrySet( );                if(entries != null) {                    Iterator<Entry<String, Object>> iterator = entries.iterator( );                    while(iterator.hasNext( )) {                    Entry<String, Object> entry =(Entry<String, Object>) iterator.next( );                    Object key = entry.getKey( );                    Object value = entry.getValue();                    System.out.println(key+":"+value);                }            }        }        return list;    }

    @RequestMapping("/user/{id}")    public Map<String,Object> getUser(@PathVariable String id){        Map<String,Object> map = null;

        List<Map<String, Object>> list = getDbType();

        for (Map<String, Object> dbmap : list) {

            Set<String> set = dbmap.keySet();

            for (String key : set) {                if(key.equals("id")){                        if(dbmap.get(key).equals(id)){                        map = dbmap;                    }                }            }        }

        if(map==null)            map = list.get(0);        return map;    }

}

运行App输入地址输出数据库数据。

2. 集成Mybatis

添加mybatis依赖，在pom.xml文件中增加如下：

<dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>1.0.0</version></dependency>

在resource文件夹下添加application.properties配置文件并输入数据库参数，如下：

spring.datasource.url=jdbc:mysql://127.0.0.1:3306/testspring.datasource.username=rootspring.datasource.password=123456spring.datasource.driver-class-name=com.mysql.jdbc.Driverspring.datasource.max-idle=10spring.datasource.max-wait=1000spring.datasource.min-idle=5spring.datasource.initial-size=5server.port=8012server.session.timeout=10server.tomcat.uri-encoding=UTF-8

依次添加mapper的接口类和xml文件，类分别如下：

AppMessageMapper.java

package com.example.demo.mapper;import java.util.List;import com.example.demo.bean.AppMessage;public interface AppMessageMapper {    int deleteByPrimaryKey(String id);    int insert(AppMessage record);    int insertSelective(AppMessage record);    AppMessage selectByPrimaryKey(String id);    int updateByPrimaryKeySelective(AppMessage record);    int updateByPrimaryKey(AppMessage record);

    List<AppMessage> selectAll();    List<AppMessage> getMessById(String id);}

AppMessageMapper.xml

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" ><mapper namespace="com.example.demo.mapper.AppMessageMapper" >  <resultMap id="BaseResultMap" type="com.example.demo.bean.AppMessage" >    <id column="id" property="id" jdbcType="VARCHAR" />    <result column="message" property="message" jdbcType="VARCHAR" />    <result column="senddate" property="senddate" jdbcType="TIMESTAMP" />  </resultMap>

  <sql id="Base_Column_List" >    id, message, senddate  </sql>  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.String" >    select     <include refid="Base_Column_List" />    from appuser_message    where id = #{id,jdbcType=VARCHAR}  </select>  <delete id="deleteByPrimaryKey" parameterType="java.lang.String" >    delete from appuser_message    where id = #{id,jdbcType=VARCHAR}  </delete>  <insert id="insert" parameterType="com.example.demo.bean.AppMessage" >    insert into appuser_message (id, message, senddate      )    values (#{id,jdbcType=VARCHAR}, #{message,jdbcType=VARCHAR}, #{senddate,jdbcType=TIMESTAMP}      )  </insert>  <insert id="insertSelective" parameterType="com.example.demo.bean.AppMessage" >    insert into appuser_message    <trim prefix="(" suffix=")" suffixOverrides="," >      <if test="id != null" >        id,      </if>      <if test="message != null" >        message,      </if>      <if test="senddate != null" >        senddate,      </if>    </trim>    <trim prefix="values (" suffix=")" suffixOverrides="," >      <if test="id != null" >        #{id,jdbcType=VARCHAR},      </if>      <if test="message != null" >        #{message,jdbcType=VARCHAR},      </if>      <if test="senddate != null" >        #{senddate,jdbcType=TIMESTAMP},      </if>    </trim>  </insert>  <update id="updateByPrimaryKeySelective" parameterType="com.example.demo.bean.AppMessage" >    update appuser_message    <set >      <if test="message != null" >        message = #{message,jdbcType=VARCHAR},      </if>      <if test="senddate != null" >        senddate = #{senddate,jdbcType=TIMESTAMP},      </if>    </set>    where id = #{id,jdbcType=VARCHAR}  </update>  <update id="updateByPrimaryKey" parameterType="com.example.demo.bean.AppMessage" >    update appuser_message    set message = #{message,jdbcType=VARCHAR},      senddate = #{senddate,jdbcType=TIMESTAMP}    where id = #{id,jdbcType=VARCHAR}  </update>

  <select id="selectAll" resultMap="BaseResultMap">    select          id, message, senddate    from appuser_message    order by senddate asc  </select>

  <select id="getMessById" resultMap="BaseResultMap" parameterType="java.lang.String">   select            id, message, senddate   from         appuser_message         where id = #{id,jdbcType=VARCHAR}    order by senddate asc    </select>

</mapper>

AppMessage.java

package com.example.demo.bean;import java.util.Date;public class AppMessage {    private String id;    private String message;    private Date senddate;    public String getId() {        return id;    }    public void setId(String id) {        this.id = id == null ? null : id.trim();    }    public String getMessage() {        return message;    }    public void setMessage(String message) {        this.message = message == null ? null : message.trim();    }    public Date getSenddate() {        return senddate;    }    public void setSenddate(Date senddate) {        this.senddate = senddate;    }}

AppMessageService.java

package com.example.demo.service;import java.util.ArrayList;import java.util.List;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;import com.example.demo.bean.AppMessage;import com.example.demo.mapper.AppMessageMapper;@Servicepublic class AppMessageService {

    @Autowired    private AppMessageMapper mapper;

    public List<AppMessage> getMessage(){         List<AppMessage> list = new ArrayList<AppMessage>();         list.add(mapper.selectByPrimaryKey("xtt"));         //list = mapper.selectAll();         return list;    }

    public List<AppMessage> getAllMessage(){         List<AppMessage> list = new ArrayList<AppMessage>();         list = mapper.selectAll();         return list;    }    public int addMessage(AppMessage appMessage) {        return mapper.insert(appMessage);    }    public List<AppMessage> getMessageById(String id) {        return mapper.getMessById(id);    }    public int delMessage(String id) {        return mapper.deleteByPrimaryKey(id);    }}

APPMessageController.java

package com.example.demo.controller;import java.util.List;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.RequestBody;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;import org.springframework.web.bind.annotation.RequestParam;import org.springframework.web.bind.annotation.RestController;import com.example.demo.bean.AppMessage;import com.example.demo.service.AppMessageService;@RestController@RequestMapping("/appmessage")public class APPMessageController {    @Autowired    private AppMessageService service;    @RequestMapping("/getThree")    public List<AppMessage> getThreeForMessage(){

        List<AppMessage> list = service.getMessage();                return list;    }

    @RequestMapping("/getAll")    public List<AppMessage> getAllMessage(){

        List<AppMessage> list = service.getAllMessage();        int num = list.size();        if(null!=list && num>3){            for (int i = 0; i < num-3; i++) {                list.remove(0);            }        }        return list;    }    @RequestMapping("/getByID")    public List<AppMessage> getMessageById(@RequestParam("id") String id){        List<AppMessage> list = service.getMessageById(id);        int num = list.size();        if(null!=list && num>5){            for (int i = 0; i < num-5; i++) {                list.remove(0);            }        }        return list;    }

    @RequestMapping(value = "/add",method = RequestMethod.POST) // 或者采用@PostMapping("/add")方法，更加节省代码的编写量    public int addMessage(@RequestBody AppMessage appMessage){        return service.addMessage(appMessage);    }

    @RequestMapping(value="/delMessageById",method=RequestMethod.POST) // 或者采用@PostMapping("/delMessageById")方法，更加节省代码的编写量    public int delMessageById(@RequestParam("id") String id){            return service.delMessage(id);    }}

问题描述

SpringBoot扫描包提示找不到mapper的问题，异常信息：

Consider defining a bean of type in your configuration

分析原因

Spring Boot项目的Bean装配默认规则是根据Application类所在的包位置从上往下扫描，“Application类”是指Spring Boot项目入口类。如果Application类所在的包为：com.yoodb.blog，则只会扫描com.yoodb.blog包及其所有子包，如果service或dao所在包不在com.yoodb.blog及其子包下，则不会被扫描。

解决方法

方式一：使用注解@ComponentScan(value=”com.yoodb.blog”)，其中，com.yoodb.blog为包路径。

方式二：将启动类Application放在上一级包中，注意的是Application启动类必须要保证在包的根目录下。