MyBatis中常用的动态SQL

说明:本文仅设置<where> 、<if>、<choose>、<set>。通过查询和更新来演示

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1.项目结构

2.pom.xml（本来这里添加Junit依赖的，然后不知道为什一下可以一下不行，所以也没有去深究，直接在项目中添加Junit支持，方便测试。。）

<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/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.lin</groupId>
  <artifactId>DynamicSQLTest</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>

  <dependencies>
  	<!-- Mybatis begin -->
	<dependency>
	    <groupId>org.mybatis</groupId>
	    <artifactId>mybatis</artifactId>
	    <version>3.3.1</version>
	</dependency>
	<!-- MyBatis end -->
  	
  	<!-- mysql begin -->
	<dependency>
	    <groupId>mysql</groupId>
	    <artifactId>mysql-connector-java</artifactId>
	    <version>5.1.30</version>
	</dependency>
  	<!-- mysql end -->
  	
  	<!-- 日志文件管理包 -->  
        <!-- log start -->  
        <dependency>  
            <groupId>log4j</groupId>  
            <artifactId>log4j</artifactId>  
            <version>1.2.17</version>  
        </dependency>  
    <!-- log end --> 
    
    <!-- Junit begin -->
	<!-- <dependency>
	    <groupId>junit</groupId>
	    <artifactId>junit</artifactId>
	    <version>4.4</version>
	</dependency> -->
    <!-- Junit end --> 
  	
  </dependencies>

  <!-- 添加项目jdk编译插件 -->
  <build>
  	<!-- 设置编译版本为1.8 -->
  	<plugins>
  		<plugin>
  			<groupId>org.apache.maven.plugins</groupId>
  			<artifactId>maven-compiler-plugin</artifactId>
  			<configuration>
  				<source>1.8</source>
  				<target>1.8</target>
  				<encoding>UTF-8</encoding>
  			</configuration>
  		</plugin>
  		<!-- 配置tomcat7的插件，如果使用maven的命令方式运行，则命令为：tomcat7:run ，
  			 而不能是tomcat:run（如果使用该命令，还是会使用maven默认的tomcat来编译运行项目）。
  			
  			可以直接使用eclipse中的tomcat来运行项目（就是原先没有使用maven时的那样运行项目就可以了，那样的话也不需要配这个插件了）。	 
  		 -->
  		<plugin>  
            <groupId>org.apache.tomcat.maven</groupId>  
            <artifactId>tomcat7-maven-plugin</artifactId>  
            <version>2.1</version>  
        </plugin>
  	</plugins>
  </build>
  
</project>

3.mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-config.dtd">
  <!--  XML 配置文件包含对 MyBatis 系统的核心设置 -->
<configuration>
	<!-- 指定 MyBatis 所用日志的具体实现 -->
	<settings>
		<setting name="logImpl" value="LOG4J"/>
		<!-- 要使延迟加载生效必须配置下面两个属性 -->
		<setting name="lazyLoadingEnabled" value="true"/>
		<setting name="aggressiveLazyLoading" value="false"/>
	</settings>
	<environments default="mysql">
	<!-- 环境配置，即连接的数据库。 -->
    <environment id="mysql">
    <!--  指定事务管理类型，type="JDBC"指直接简单使用了JDBC的提交和回滚设置 -->
      <transactionManager type="JDBC"/>
      <!--  dataSource指数据源配置，POOLED是JDBC连接对象的数据源连接池的实现。 -->
      <dataSource type="POOLED">
        <property name="driver" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://127.0.0.1:3306/maven"/>
        <property name="username" value="root"/>
        <property name="password" value="546784"/>
      </dataSource>
    </environment>
  </environments>
  <!-- mappers告诉了MyBatis去哪里找持久化类的映射文件 -->
  <mappers>
  	<package name="org.fkit.mapper"/>
  </mappers>
</configuration>

3.实体类Employee.java 和SQL脚本语句

/**
 * 
 * SQL脚本：
 * 
 CREATE TABLE tb_employee (
  ID INT(11) PRIMARY KEY AUTO_INCREMENT,
  loginname VARCHAR(18),
  PASSWORD VARCHAR(18),
  NAME VARCHAR(18) DEFAULT NULL,
  SEX CHAR(2) DEFAULT NULL,
  AGE INT(11) DEFAULT NULL,
  phone VARCHAR(21),
  sal DOUBLE,
  state VARCHAR(18)
 )
 
 INSERT INTO tb_employee(loginname,PASSWORD,NAME,sex,age,phone,sal,state)
 VALUES('jack','123456','杰克','男',26,'13902019999',9800,'ACTIVE');
  INSERT INTO tb_employee(loginname,PASSWORD,NAME,sex,age,phone,sal,state)
 VALUES('rose','123456','露丝','女',21,'13902018888',6800,'ACTIVE');


 * */

public class Employee implements Serializable {
	private static final long serialVersionUID = 1L;
	
	private Integer id;			 // 主键id
	private String loginname;	 // 登录名
	private String password;	 // 密码
	private String name;		 // 真实姓名
	private String sex;			 // 性别
	private Integer age;		 // 年龄
	private String phone;		 // 电话
	private Double sal;		     // 薪水
	private String state;	 	 // 状态
	
	//省略set和get方法……
	
	public String toString() {
		return "Employee [id=" + id + ", loginname=" + loginname
				+ ", password=" + password + ", name=" + name + ", sex=" + sex
				+ ", age=" + age + ", phone=" + phone + ", sal=" + sal
				+ ", state=" + state + "]";
	}

}

4.EmployeeMapper.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="org.fkit.mapper.EmployeeMapper">
	<select id="selectEmployeeByIdLike" resultType="org.fkit.domain.Employee">
		select * from tb_employee
			<where>
				state = 'ACTIVE'
				<!-- 
					如果传入了id，就根据id查询；没有传入id就根据loginname和password查询；否则查询sex等于男的数据。
				 -->
				 <choose>
				 	<when test="id!=null and id!=''">
				 		and id = #{id}
				 	</when>
				 	<when test="loginname!=null and loginname!=''  and password!=null and password!=''">
				 		and loginname = #{loginname} and password = #{password}
				 	</when>
				 	<otherwise>
				 		and sex = '男'
				 	</otherwise>
				 </choose>
			</where>
			<!-- where和if测试的方式一
			<where>
				<if test="state!=null and state!=''">
					state = 'ACTIVE'
				</if>
				<if test="id!=null and id!=''">
					and id = #{id}
				</if>
			</where>
			 -->
			
			<!-- where和if测试的方式二
			<where>
				<if test="state!=null and state!='' and id!=null and id!=''">
					and state = 'ACTIVE'and id = #{id}
				</if>
			</where> 
			--> 			

	</select>
	
	<!-- 根据id查询Employee信息(因为一般在执行更新操作时会先查出用户信息，此处模拟) -->
	<select id="selectEmployeeWithId" parameterType="int" resultType="org.fkit.domain.Employee">
		select * from tb_employee
			where id = #{id}
	</select>
	
	<!-- 动态更新员工信息 -->
	<update id="updateEmployeeIfNecessary" parameterType="org.fkit.domain.Employee">
		update tb_employee
		<set>
			<if test="loginname!=null and loginname!=''">
				loginname = #{loginname},
			</if>
			<if test="password!=null and password!=''">
				password = #{password},
			</if>
			<if test="name!=null and name!=''">
				name = #{name},
			</if>
			<if test="sex!=null and sex!=''">
				sex = #{sex},
			</if>
			<if test="age!=null and age!=''">
				age = #{age},
			</if>
			<if test="phone!=null and phone!=''">
				phone = #{phone},
			</if>
			<if test="sal!=null and sal!=''">
				sal = #{sal},
			</if>
			<if test="state!=null and state!=''">
				state = #{state},
			</if>
		</set>
		<!-- <where>
			<if test="id!=null and id!=''">
				id = #{id}
			</if>
		</where> -->
		where 
			id=#{id}
		
	</update>
</mapper>

5.EmployeeMapper.java

package org.fkit.mapper;


import java.util.HashMap;
import java.util.List;

import org.fkit.domain.Employee;

public interface EmployeeMapper {
	public List<Employee> selectEmployeeByIdLike(HashMap<String, Object>params);

	public Employee selectEmployeeWithId(int id);
	
	public void updateEmployeeIfNecessary(Employee e);
}

6.测试类DynamicSQLTest.java

import java.io.InputStream;
import java.util.HashMap;
import java.util.List;


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.fkit.domain.Employee;
import org.fkit.mapper.EmployeeMapper;
import org.junit.Test;


public class DynamicSQLTest {

	//SQL动态查询操作
	@Test
	public void selectTest() throws Exception{
		//读取mybatis-config.xml文件
		InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
		//初始化mybatis，创建SQLSessionFactory类的实例
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
		//创建SqlSession实例
		SqlSession sqlSession = sqlSessionFactory.openSession();
		
		DynamicSQLTest d = new DynamicSQLTest();
		d.testSelectEmployeeByIdLike(sqlSession);
		//提交事务
		sqlSession.commit();
		//关闭session
		sqlSession.close();
		
	}
	
	public void testSelectEmployeeByIdLike(SqlSession session){
		//获得EmployeeMapper接口的代理对象
		EmployeeMapper em = session.getMapper(EmployeeMapper.class);
		//创建一个HashMap存储参数
		HashMap<String,Object> params = new HashMap<String,Object>();
		/**以下用于单独测试where标签使用*/
//		//设置id属性
//		params.put("id", 1);
//		//设置state属性
//		params.put("state", "ACTIVE");
		/**以下用于单独测试choose标签使用*/
		params.put("id", 1);
		params.put("loginname", "jack");
		params.put("password", "123456");
		//调用EmployeeMapper接口的selectEmployeeByIdLike方法
		List<Employee> list = em.selectEmployeeByIdLike(params);
		//查看结果
		list.forEach(employee -> System.out.println(employee));
	}
	
	
	//动态SQL更新操作
	@Test
	public void updateTest() throws Exception{
		//读取mybatis-config.xml文件
		InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
		//初始化mybatis，创建SQLSessionFactory类的实例
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
		//创建SqlSession实例
		SqlSession sqlSession = sqlSessionFactory.openSession();
				
		DynamicSQLTest d = new DynamicSQLTest();
		d.testUpdateEmployee(sqlSession);
		//提交事务
		sqlSession.commit();
		//关闭session
		sqlSession.close();		
	}
	
	public void testUpdateEmployee(SqlSession sqlSession){
		EmployeeMapper em = sqlSession.getMapper(EmployeeMapper.class);
		//查询id为4的员工信息
		Employee employee = em.selectEmployeeWithId(4);
		System.out.println(employee);
		//设置需要修改的属性
		employee.setLoginname("Mary");
		employee.setPassword("123");
		employee.setName("玛丽");
		//更新员工信息
		em.updateEmployeeIfNecessary(employee);
		
		//查询id为4的员工信息
		Employee employee2 = em.selectEmployeeWithId(4);
		System.out.println(employee2);
	}
}

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测试运行，以下是动态更新操作