mybatis--MyBatis动态SQL语句

mybatis 的动态sql语句是基于OGNL表达式的。可以方便的在 sql 语句中实现某些逻辑. 总体说来mybatis 动态SQL 语句主要有以下几类:
1. if 语句 (简单的条件判断)
2. choose (when,otherwize) ,相当于java 语言中的 switch ,与 jstl 中的choose 很类似.
3. trim (对包含的内容加上 prefix,或者 suffix 等，前缀，后缀)
4. where (主要是用来简化sql语句中where条件判断的，能智能的处理 and or ,不必担心多余导致语法错误)
5. set (主要用于更新时)
6. foreach (用于mybatis语句查询)

 

1.if语句(简单的条件判断)

（1）数据库my的user表数据为：

 

 

（2）首先创建一个mybatis项目，mybatis_008

 

（3）建立com.zk.dao包下的IUser接口：

IUser.java

package com.zk.dao;

import org.apache.ibatis.annotations.Param;
import com.zk.pojo.User;

public interface IUser {
		public User findUserWithNameLike(@Param("id")int id, @Param("name")String name);
}

（4）在com.zk.pojo包下建立User实现IUser接口中的方法，并配置UserMapper.xml

User.java

package com.zk.pojo;

public class User {
	private int id;
	private String name;
	private String level;
	private String phone;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getLevel() {
		return level;
	}
	public void setLevel(String level) {
		this.level = level;
	}
	public String getPhone() {
		return phone;
	}
	public void setPhone(String phone) {
		this.phone = phone;
	}
	@Override
	public String toString() {
		return "User [id=" + id + ", name=" + name + ", level=" + level
				+ ", phone=" + phone + "]";
	}
}

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="com.zk.dao.IUser">
<select id="findUserWithNameLike" resultType="User">
  SELECT * FROM user 
  WHERE id = #{id} <if test="name!= null">
    AND name like #{name}
  </if>
</select>
</mapper>

（5）配置config/configure.xml

configure.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>
<typeAliases>
<typeAlias alias="User" type="com.zk.pojo.User" />
</typeAliases>

<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/my"/>
		<property name="username" value="root"/>
		<property name="password" value="123456"/>
		</dataSource>
		</environment>
	</environments>

	<mappers>
	     <!-- // power by http://www.yiibai.com -->
	     <mapper resource="com/zk/pojo/UserMapper.xml" />
	</mappers>
</configuration>

（6）实现main函数

MainApp.java

package Main;

import java.io.IOException;
import java.io.Reader;

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 com.zk.dao.IUser;
import com.zk.pojo.User;

public class MainApp {
	private static SqlSessionFactory sqlsessionfactory;
	private static Reader reader;
	
	static{
		try {
			reader=Resources.getResourceAsReader("config/configure.xml");
			sqlsessionfactory=new SqlSessionFactoryBuilder().build(reader);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public SqlSessionFactory getSqlSessionFactory()
	{
		return sqlsessionfactory;
	}
	
	public static void main(String[]args)
	{
		select(1,"c");
	}
	
	public static void select(int id,String name){
		//获取session连接
		SqlSession session=sqlsessionfactory.openSession();
		//获取mapper
		IUser usermap=session.getMapper(IUser.class);
		//selectAllUser();
		User user = usermap.findUserWithNameLike(id, name);
		//执行查询
		System.out.println(user.toString());
		session.commit();
		//selectAllUser();
	}
}

　　Main执行结果如下：

2. where (主要是用来简化sql语句中where条件判断的，能智能的处理 and or ,不必担心多余导致语法错误)

(1) 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="com.zk.dao.IUser">
<select id="findUserWithNameLike" resultType="User">
  SELECT * FROM user    
  <where>  <if test="id!=null">id like #{id}</if>
  <if test="name!=null">AND name like #{name}</if>
  </where>
  </select>
</mapper>

 

运行结果如下：

 

3. choose (when,otherwize) ,相当于java 语言中的 switch ,与 jstl 中的choose 很类似.

同样原始的数据库，仅更改pojo层的UserMapper.xml，如下所示：

<?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.zk.dao.IUser">
<select id="findUserWithNameLike" resultType="User">
  SELECT * FROM user where
    <choose>
    <when test="id!=null">
    id like #{id}
    </when>
    <when test="name!=null">
    AND name like #{name}
    </when>
    </choose>
  
</select>
</mapper>

　运行后得到的结果如下图所示：

4. set (主要用于更新时)

（1）IUser.java

package com.zk.dao;



import com.zk.pojo.User;


public interface IUser {
	public User updateUser(User user);
}

（2）UserMapper.xml和User.java

User.java

package com.zk.pojo;

public class User {
	private int id;
	private String name;
	private String level;
	private String phone;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getLevel() {
		return level;
	}
	public void setLevel(String level) {
		this.level = level;
	}
	public String getPhone() {
		return phone;
	}
	public void setPhone(String phone) {
		this.phone = phone;
	}
	@Override
	public String toString() {
		return "User [id=" + id + ", name=" + name + ", level=" + level
				+ ", phone=" + phone + "]";
	}
}

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="com.zk.dao.IUser">
<update id="updateUser" parameterType="User">
update user
<set>
<if test="name!=null">name=#{name},</if>
<if test="level!=null">level=#{level},</if>
<if test="phone!=null">phone=#{phone}</if>
</set>
where id=#{id}
</update>
</mapper>

（3）configure.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>
<typeAliases>
<typeAlias alias="User" type="com.zk.pojo.User" />
</typeAliases>

<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/my"/>
		<property name="username" value="root"/>
		<property name="password" value="123456"/>
		</dataSource>
		</environment>
	</environments>

	<mappers>
	     <mapper resource="com/zk/pojo/UserMapper.xml" />
	</mappers>
</configuration>

（4）Main.java

package Main;

import java.io.IOException;
import java.io.Reader;

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 com.zk.dao.IUser;
import com.zk.pojo.User;

public class MainApp {
	private static SqlSessionFactory sqlsessionfactory;
	private static Reader reader;
	
	static{
		try {
			reader=Resources.getResourceAsReader("config/configure.xml");
			sqlsessionfactory=new SqlSessionFactoryBuilder().build(reader);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public SqlSessionFactory getSqlSessionFactory()
	{
		return sqlsessionfactory;
	}
	
	public static void main(String[]args)
	{
		SqlSession session=sqlsessionfactory.openSession();
		User user=new User();
		user.setId(1);
		user.setName("a");
		user.setLevel("a");
		user.setPhone("137298647");
		
		session.update("updateUser",user);
		session.commit();
	}
}　

运行结果如下：　

 

 5. trim (对包含的内容加上 prefix,或者 suffix 等，前缀，后缀)

 IUser.java

package com.zk.dao;

import org.apache.ibatis.annotations.Param;
import com.zk.pojo.User;

public interface IUser {
	public User findUserWithNameLike(@Param("id")int id, @Param("name")String name);
}

User.java

package com.zk.pojo;

public class User {
	private int id;
	private String name;
	private String level;
	private String phone;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getLevel() {
		return level;
	}
	public void setLevel(String level) {
		this.level = level;
	}
	public String getPhone() {
		return phone;
	}
	public void setPhone(String phone) {
		this.phone = phone;
	}
	@Override
	public String toString() {
		return "User [id=" + id + ", name=" + name + ", level=" + level
				+ ", phone=" + phone + "]";
	}
}

　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="com.zk.dao.IUser">
<select id="findUserWithNameLike" resultType="User">
  SELECT * FROM user  
<trim prefix="WHERE" prefixOverrides="AND">
	<if test="id!=null">
	  id=#{id}
	</if> 
	<if test="name!= null">
	  AND name like #{name}
	</if>
</trim>
</select>
</mapper>

MainApp.java

package Main;

import java.io.IOException;
import java.io.Reader;

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 com.zk.dao.IUser;
import com.zk.pojo.User;

public class MainApp {
	    private static SqlSessionFactory sqlsessionfactory;
	    private static Reader reader;
	     
	    static{
	        try {
	            reader=Resources.getResourceAsReader("config/configure.xml");
	            sqlsessionfactory=new SqlSessionFactoryBuilder().build(reader);
	        } catch (IOException e) {
	            // TODO Auto-generated catch block
	            e.printStackTrace();
	        }
	    }
	     
	    public SqlSessionFactory getSqlSessionFactory()
	    {
	        return sqlsessionfactory;
	    }
	     
	    public static void main(String[]args)
	    {
	        select(1,"a");
	    }
	     
	    public static void select(int id,String name){
	        //获取session连接
	        SqlSession session=sqlsessionfactory.openSession();
	        //获取mapper
	        IUser usermap=session.getMapper(IUser.class);
	        //selectAllUser();
	        User user = usermap.findUserWithNameLike(id, name);
	        //执行查询
	        System.out.println(user.toString());
	        session.commit();
	        //selectAllUser();
	    }
}

执行结果如下：

 

 6. foreach (用于mybatis语句查询)

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="com.zk.dao.IUser">
<select id="findUsersWithIdforeach" resultType="User">
  SELECT * FROM user  
  <where>id in
  <foreach collection="list" item="item" open="(" close=")" separator=",">
  #{item}
  </foreach>
  </where>
</mapper>

IUser.java

package com.zk.dao;

import java.util.List;
import org.apache.ibatis.annotations.Param;

import com.zk.pojo.User;

public interface IUser {
	public List<User> findUsersWithIdforeach(@Param("list")List<Integer> list);
}

Main.java

package Main;

import java.io.IOException;
import java.io.Reader;
import java.util.ArrayList;
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 com.zk.dao.IUser;
import com.zk.pojo.User;

public class MainApp {
	 private static SqlSessionFactory sqlsessionfactory;
	    private static Reader reader;
	     
	    static{
	        try {
	            reader=Resources.getResourceAsReader("config/configure.xml");
	            sqlsessionfactory=new SqlSessionFactoryBuilder().build(reader);
	        } catch (IOException e) {
	            // TODO Auto-generated catch block
	            e.printStackTrace();
	        }
	    }
	     
	    public SqlSessionFactory getSqlSessionFactory()
	    {
	        return sqlsessionfactory;
	    }
	     
	    public static void main(String[]args)
	    {
	        select(1,"a");
	    }
	     
	    public static void select(int id,String name){
	        //获取session连接
	        SqlSession session=sqlsessionfactory.openSession();
	        //获取mapper
	        IUser usermap=session.getMapper(IUser.class);
	        //selectAllUser();
	        List ids=new ArrayList();
	        ids.add(1);
	        ids.add(2);
	        ids.add(3);
	        ids.add(4);
	        //执行查询
	        //System.out.println(user.toString());
	        List<User> users=usermap.findUsersWithIdforeach(ids);
	        for(User u:users)
	        {
	        	System.out.println(u);
	        }
	        session.commit();
	        //selectAllUser();
	    }
}

程序运行结果：

数据库中数据：