mybatis学习笔记(3)-入门程序一

标签： mybatis

[TOC]

工程结构

在IDEA中新建了一个普通的java项目，新建文件夹lib,加入jar包,工程结构如图。

• log4j.properties

# Global logging configuration
log4j.rootLogger=DEBUG, stdout
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

• SqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><!-- 和spring整合后 environments配置将废除--><environments default="development"><environment id="development"><!-- 使用jdbc事务管理，事务控制由mybatis--><transactionManager type="JDBC" /><!-- 数据库连接池,由mybatis管理--><dataSource type="POOLED"><property name="driver" value="com.mysql.jdbc.Driver" /><property name="url" value="jdbc:mysql://120.25.162.238:3306/mybatis001?characterEncoding=utf-8" /><property name="username" value="root" /><property name="password" value="123" /></dataSource></environment></environments></configuration>

映射文件

• sqlmap/User.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!-- namespace 命名空间，作用就是对sql进行分类化管理,理解为sql隔离注意：使用mapper代理方法开发，namespace有特殊重要的作用-->
<mapper namespace="test"><!-- 在映射文件中配置很多sql语句 --><!--需求:通过id查询用户表的记录 --><!-- 通过select执行数据库查询id:标识映射文件中的sql，称为statement的id将sql语句封装到mappedStatement对象中，所以将id称为statement的idparameterType:指定输入参数的类型#{}标示一个占位符,#{value}其中value表示接收输入参数的名称，如果输入参数是简单类型，那么#{}中的值可以任意。resultType：指定sql输出结果的映射的java对象类型，select指定resultType表示将单条记录映射成java对象--><select id="findUserById" parameterType="int" resultType="com.iot.mybatis.po.User">SELECT * FROM  user  WHERE id=#{value}</select><!-- 根据用户名称模糊查询用户信息，可能返回多条resultType：指定就是单条记录所映射的java对象类型${}:表示拼接sql串，将接收到参数的内容不加任何修饰拼接在sql中。使用${}拼接sql，引起 sql注入${value}：接收输入参数的内容，如果传入类型是简单类型，${}中只能使用value--><select id="findUserByName" parameterType="java.lang.String" resultType="com.iot.mybatis.po.User">SELECT * FROM user WHERE username LIKE '%${value}%'</select></mapper>

在sqlMapConfig.xml中加载User.xml

<!-- 加载映射文件-->
<mappers><mapper resource="sqlmap/User.xml"/>
</mappers>

程序代码

• po类User.java

package com.iot.mybatis.po;import java.util.Date;/*** Created by Administrator on 2016/2/21.*/
public class User {//属性名要和数据库表的字段对应private int id;private String username;// 用户姓名private String sex;// 性别private Date birthday;// 生日private String address;// 地址public int getId() {return id;}public void setId(int id) {this.id = id;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}@Overridepublic String toString() {return "User [id=" + id + ", username=" + username + ", sex=" + sex+ ", birthday=" + birthday + ", address=" + address + "]";}
}

• 测试代码

package com.iot.mybatis.first;import com.iot.mybatis.po.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;import java.io.IOException;
import java.io.InputStream;
import java.util.List;/*** Created by Administrator on 2016/2/23.*/
public class MybatisFirst {//根据id查询用户信息，得到一条记录结果@Testpublic void findUserByIdTest() throws IOException{// mybatis配置文件String resource = "SqlMapConfig.xml";// 得到配置文件流InputStream inputStream =  Resources.getResourceAsStream(resource);//创建会话工厂，传入mybatis配置文件的信息SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);// 通过工厂得到SqlSessionSqlSession sqlSession = sqlSessionFactory.openSession();// 通过SqlSession操作数据库// 第一个参数：映射文件中statement的id，等于=namespace+"."+statement的id// 第二个参数：指定和映射文件中所匹配的parameterType类型的参数// sqlSession.selectOne结果 是与映射文件中所匹配的resultType类型的对象// selectOne查询出一条记录User user = sqlSession.selectOne("test.findUserById", 1);System.out.println(user);// 释放资源sqlSession.close();}// 根据用户名称模糊查询用户列表@Testpublic void findUserByNameTest() throws IOException {// mybatis配置文件String resource = "SqlMapConfig.xml";// 得到配置文件流InputStream inputStream = Resources.getResourceAsStream(resource);// 创建会话工厂，传入mybatis的配置文件信息SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);// 通过工厂得到SqlSessionSqlSession sqlSession = sqlSessionFactory.openSession();// list中的user和映射文件中resultType所指定的类型一致List<User> list = sqlSession.selectList("test.findUserByName", "小明");System.out.println(list);sqlSession.close();}}

输出：

• findUserByIdTest()

DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Created connection 1857815974.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ebc05a6]
DEBUG [main] - ==>  Preparing: SELECT * FROM user WHERE id=?
DEBUG [main] - ==> Parameters: 1(Integer)
DEBUG [main] - <==      Total: 1
User [id=1, username=王五, sex=2, birthday=null, address=null]
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ebc05a6]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ebc05a6]
DEBUG [main] - Returned connection 1857815974 to pool.

• findUserByNameTest()

DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Created connection 1596467899.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@5f282abb]
DEBUG [main] - ==>  Preparing: SELECT * FROM user WHERE username LIKE '%小明%'
DEBUG [main] - ==> Parameters:
DEBUG [main] - <==      Total: 3
[User [id=16, username=张小明, sex=1, birthday=null, address=河南郑州], User [id=22, username=陈小明, sex=1, birthday=null, address=河南郑州], User [id=25, username=陈小明, sex=1, birthday=null, address=河南郑州]]
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@5f282abb]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@5f282abb]
DEBUG [main] - Returned connection 1596467899 to pool.

总结

• parameterType

在映射文件中通过parameterType指定输入参数的类型

• resultType

在映射文件中通过resultType指定输出结果的类型

• #{}和${} #{}表示一个占位符号; ${}表示一个拼接符号，会引起sql注入，所以不建议使用

• selectOne和selectList selectOne表示查询一条记录进行映射，使用selectList也可以使用，只不过只有一个对象 selectList表示查询出一个列表(参数记录)进行映射，不嗯能够使用selectOne查，不然会报下面的错:

org.apache.ibatis.exceptions.TooManyResultsException: Expected one result (or null) to be returned by selectOne(), but found: 3

作者@brianway更多文章：个人网站 | CSDN | oschina