MyBatis研习录(11)——MyBatis动态SQL

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版权声明

• 本文原创作者：谷哥的小弟
• 作者博客地址：http://blog.csdn.net/lfdfhl

概述

动态SQL是MyBatis 的强大特性，利用动态SQL可以极大的优化SQL语句的编写及其处理。

数据准备

CREATE TABLE user(
id INT PRIMARY KEY auto_increment,
username VARCHAR(50),
password VARCHAR(50),
gender VARCHAR(10)
);

INSERT INTO user(username,password,gender) VALUES("lucy","123456","female");
INSERT INTO user(username,password,gender) VALUES("momo","234567","female");
INSERT INTO user(username,password,gender) VALUES("xixi","345678","female");
INSERT INTO user(username,password,gender) VALUES("pepe","456123","female");

SELECT * FROM user;

搭建开发环境

创建普通的Java工程，结构如下：

User

package cn.com.pojo;
/**
* 本文作者：谷哥的小弟
* 博客地址：http://blog.csdn.net/lfdfhl
*/
public class User {
private Integer id;
private String username;
private String password;
private String gender;
public User() {

}

public User(Integer id, String username, String password, String gender) {
super();
this.id = id;
this.username = username;
this.password = password;
this.gender = gender;
}

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getUsername() {
return username;
}

public void setUsername(String username) {
this.username = username;
}

public String getPassword() {
return password;
}

public void setPassword(String password) {
this.password = password;
}

public String getGender() {
return gender;
}

public void setGender(String gender) {
this.gender = gender;
}

@Override
public String toString() {
return "User [id=" + id + ", username=" + username + ", password=" + password + ", gender=" + gender + "]";
}

}

UserMapper.java

package cn.com.mapper;

import java.util.List;
import org.apache.ibatis.annotations.Param;
import cn.com.pojo.User;
/**
* 本文作者：谷哥的小弟
* 博客地址：http://blog.csdn.net/lfdfhl
*/
public interface UserMapper {

//测试动态SQL语句if
public List<User> queryUserWithIf(@Param("username")String username,@Param("password")String password);

//测试动态SQL语句where
public List<User> queryUserWithWhere(@Param("username")String username,@Param("password")String password);

//测试动态SQL语句choose
public List<User> queryUserWithChoose(@Param("username")String username,@Param("password")String password);

//测试动态SQL语句set
public int updateUserWithSet(User user);

//测试动态SQL语句trim
public int updateUserWithTrim(User user);

//测试动态SQL语句bind
public List<User> queryUserWithBind(@Param("username")String username);

//测试动态SQL语句foreach
public List<User> queryUserWithForeach(@Param("userIDList")List<Integer> userIDList);

//测试动态SQL语句include
public List<User> queryUserWithInclude(@Param("username")String username,@Param("password")String password);

}

常用动态SQL

if

if用于进行条件判断，其test属性用于指定判断条件。

注意事项：
在test的属性值中不必再使用占位符#{ }

where

where主要用于用于管理where子句，其主要作用如下：

• 1、如果没有where子句则不生成where关键字
• 2、如果有where子句则自动添加where关键字
• 3、如果where子句第一个条件中有and则将其去除

choose

choose常与when、otherwise配合使用用于分支选择，其使用方式和作用非常类似于switch case default语句。

set

set用于维护update语句中的set子句，其主要作用如下：

• 1、满足条件时, 自动添加set关键字
• 2、不满足条件时, 不会生成set关键字
• 3、删除set子句中多余的逗号

trim

trim用于在SQL语句前后添加或删除一些内容，其属性作用如下：

• 1、prefix：在SQL语句前面添加内容
• 2、prefixOverrides：从SQL语句前面去除内容
• 3、suffix：向SQL语句后面添加内容
• 4、suffixOverrides：从SQL语句后面去除内容

bind

bind用于对数据进行再加工，常用于模糊查询。

foreach

foreach用于在SQL语句中遍历集合参数，常在in查询中使用；，其属性作用如下：

• 1、collection：设置待遍历集合
• 2、open：设置开始符号
• 3、item：迭代变量
• 4、separator：分隔符
• 5、close：设置结束符号

include

include常与sql配合使用；其中，sql抽取公用SQL语句include引用该语句。

UserMapper.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="cn.com.mapper.UserMapper">

<!-- 测试动态SQL语句if -->
<select id="queryUserWithIf" resultType="cn.com.pojo.User">
select * from user where 1=1
<if test="username !=null and username !=''">
and username=#{username}
</if>
<if test="password !=null and password !=''">
and password=#{password}
</if>
</select>

<!-- 测试动态SQL语句where -->
<select id="queryUserWithWhere" resultType="cn.com.pojo.User">
select * from user
<where>
<if test="username !=null and username !=''">
and username=#{username}
</if>
<if test="password !=null and password !=''">
and password=#{password}
</if>
</where>
</select>

<!-- 测试动态SQL语句choose -->
<select id="queryUserWithChoose" resultType="cn.com.pojo.User">
select * from user
<where>
<choose>
<when test="username !=null and username !=''">
and username=#{username}
</when>
<when test="password !=null and password !=''">
and password=#{password}
</when>
<otherwise>
and username like concat('%','lu','%')
</otherwise>
</choose>
</where>
</select>

<!-- 测试动态SQL语句set -->
<update id="updateUserWithSet" parameterType="cn.com.pojo.User">
update user
<set>
<if test="username !=null and username !=''">
username=#{username},
</if>
<if test="password !=null and password !=''">
password=#{password},
</if>
<if test="gender !=null and gender !=''">
gender=#{gender}
</if>
</set>
where id=#{id}
</update>

<!-- 测试动态SQL语句trim -->
<update id="updateUserWithTrim" parameterType="cn.com.pojo.User">
update user
<trim prefix="set" suffixOverrides=",,,">
username=#{username},,,
</trim>
where id=#{id}
</update>

<!-- 测试动态SQL语句bind -->
<select id="queryUserWithBind" resultType="cn.com.pojo.User">
select * from user
<where>
<if test="username !=null and username !=''">
<bind name="username" value="'%'+username+'%'"/>
username like #{username}
</if>
</where>
</select>

<!-- 测试动态SQL语句foreach -->
<select id="queryUserWithForeach" parameterType="list" resultType="cn.com.pojo.User">
select * from user where id in
<foreach collection="userIDList" open="(" separator="," close=")" item="userID">
#{userID}
</foreach>
</select>

<!-- 测试动态SQL语句include -->
<sql id="columns">id,username,password,gender</sql>
<select id="queryUserWithInclude" resultType="cn.com.pojo.User">
select <include refid="columns"/> from user
<where>
<if test="username !=null and username !=''">
and username=#{username}
</if>
<if test="password !=null and password !=''">
and password=#{password}
</if>
</where>
</select>

</mapper>

MybatisTest

package cn.com.test;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.Iterator;
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.junit.Test;
import cn.com.mapper.UserMapper;
import cn.com.pojo.User;
/**
* 本文作者：谷哥的小弟
* 博客地址：http://blog.csdn.net/lfdfhl
*/
public class MybatisTest {

static SqlSessionFactory sqlSessionFactory = null;

public static SqlSessionFactory getSqlSessionFactory() {
try {
if (sqlSessionFactory == null) {
InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
}
return sqlSessionFactory;
} catch (Exception e) {
// TODO: handle exception
} finally {

}
return null;
}

@Test
public void testQueryUserWithIf() {
//获取SqlSession
SqlSession sqlSession=getSqlSessionFactory().openSession();
//利用SqlSession得到UserMapper
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//利用SqlSession执行数据操作
List<User> userList = userMapper.queryUserWithIf("lucy", "123456");
//List<User> userList = userMapper.queryUserWithIf("", "");
//List<User> userList = userMapper.queryUserWithIf("lucy", "");
//List<User> userList = userMapper.queryUserWithIf("", "123456");
Iterator<User> iterator = userList.iterator();
while(iterator.hasNext()) {
User user = iterator.next();
System.out.println(user);
}
//关闭SqlSession
sqlSession.close();
}

@Test
public void testQueryUserWithWhere() {
//获取SqlSession
SqlSession sqlSession=getSqlSessionFactory().openSession();
//利用SqlSession得到UserMapper
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//利用SqlSession执行数据操作
List<User> userList = userMapper.queryUserWithWhere("lucy", "123456");
//List<User> userList = userMapper.queryUserWithWhere("", "");
//List<User> userList = userMapper.queryUserWithWhere("lucy", "");
//List<User> userList = userMapper.queryUserWithWhere("", "123456");
Iterator<User> iterator = userList.iterator();
while(iterator.hasNext()) {
User user = iterator.next();
System.out.println(user);
}
//关闭SqlSession
sqlSession.close();
}

@Test
public void testQueryUserWithChoose() {
//获取SqlSession
SqlSession sqlSession=getSqlSessionFactory().openSession();
//利用SqlSession得到UserMapper
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//利用SqlSession执行数据操作
List<User> userList = userMapper.queryUserWithChoose("lucy", "123456");
//List<User> userList = userMapper.queryUserWithChoose("", "");
//List<User> userList = userMapper.queryUserWithChoose("lucy", "");
//List<User> userList = userMapper.queryUserWithChoose("", "123456");
Iterator<User> iterator = userList.iterator();
while(iterator.hasNext()) {
User user = iterator.next();
System.out.println(user);
}
//关闭SqlSession
sqlSession.close();
}

@Test
public void testUpdateUserWithSet() {
//获取SqlSession
SqlSession sqlSession=getSqlSessionFactory().openSession();
//利用SqlSession得到UserMapper
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//利用SqlSession执行数据操作
User user=new User(1, "tutu", "666999", "male");
int result=userMapper.updateUserWithSet(user);
System.out.println(result);
//提交
sqlSession.commit();
//关闭SqlSession
sqlSession.close();
}

@Test
public void testUpdateUserWithTrim() {
//获取SqlSession
SqlSession sqlSession=getSqlSessionFactory().openSession();
//利用SqlSession得到UserMapper
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//利用SqlSession执行数据操作
User user=new User(1, "wawa", "666666", "male");
int result=userMapper.updateUserWithTrim(user);
System.out.println(result);
//提交
sqlSession.commit();
//关闭SqlSession
sqlSession.close();
}

@Test
public void testQueryUserWithBind() {
//获取SqlSession
SqlSession sqlSession=getSqlSessionFactory().openSession();
//利用SqlSession得到UserMapper
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//利用SqlSession执行数据操作
List<User> userList = userMapper.queryUserWithBind("xi");
Iterator<User> iterator = userList.iterator();
while(iterator.hasNext()) {
User user = iterator.next();
System.out.println(user);
}
//关闭SqlSession
sqlSession.close();
}

@Test
public void testQueryUserWithForeach() {
//获取SqlSession
SqlSession sqlSession=getSqlSessionFactory().openSession();
//利用SqlSession得到UserMapper
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//利用SqlSession执行数据操作
List<Integer> userIDList=new ArrayList<Integer>();
userIDList.add(1);
userIDList.add(2);
userIDList.add(3);
List<User> userList = userMapper.queryUserWithForeach(userIDList);
Iterator<User> iterator = userList.iterator();
while(iterator.hasNext()) {
User user = iterator.next();
System.out.println(user);
}
//关闭SqlSession
sqlSession.close();
}

@Test
public void testQueryUserWithInclude() {
//获取SqlSession
SqlSession sqlSession=getSqlSessionFactory().openSession();
//利用SqlSession得到UserMapper
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
//利用SqlSession执行数据操作
List<User> userList = userMapper.queryUserWithInclude("pepe", "456123");
Iterator<User> iterator = userList.iterator();
while(iterator.hasNext()) {
User user = iterator.next();
System.out.println(user);
}
//关闭SqlSession
sqlSession.close();
}

}

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

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">
<configuration>
<!-- 配置数据源 -->
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatisDatabase"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>

<!-- 配置mapper -->
<mappers>
<mapper resource="cn/com/pojo/UserMapper.xml"/>
</mappers>

</configuration>