文章目录

文章目录

• 文章目录
• • @[TOC](文章目录)
• 一、动态sql-if
• 二、动态sql-foreach
• 三、sql片段抽取
• • 1.sql语句抽取
  • 2.引入SQL语句
• 四、案例
• • 1.pom.xml
  • 2.jdbc.properties
  • 3.mybatis-config.xml
  • 4.User
  • 5.UserMapper
  • 6.UserMapper.xml
  • 7.Test

一、动态sql-if

 <select id="findCondition" parameterType="user" resultType="user">
      select * from user
     <where>
         <if test="id!=0">
             and id=#{id}
         </if>
         <if test="username!=null">
             and username=#{username}
         </if>
         <if test="password!=null">
             and password=#{password}
         </if>
     </where>

    </select>
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二、动态sql-foreach

 <select id="findBuIds" parameterType="list" resultType="user">
        select * from user
        <where>
            <foreach collection="list" open="id in(" close=")" item="id" separator=",">
                #{id}
            </foreach>
        </where>
    </select>
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三、sql片段抽取

1.sql语句抽取

<!-- sql语句抽取-->
    <sql id="sqls"> select * from user</sql>
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2.引入SQL语句

 <include refid="sqls"></include>
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四、案例

1.pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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>org.example</groupId>
    <artifactId>MyBatis-Dao</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.32</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>
</project>
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2.jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatisthree
jdbc.username=root
jdbc.password=root
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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">
<!--configuration core file-->
       <configuration>
    <!--通过properties标签添加properties文件-->
    <properties resource="jdbc.properties"></properties>
    <!--自定义别名-->
    <typeAliases>
        <typeAlias type="com.study.domain.User" alias="user"></typeAlias>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--加载sql映射文件-->
    <mappers>
        <mapper resource="com/study/dao/UserMapper.xml"/>
    </mappers>
</configuration>
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4.User

package com.study.domain;

public class User {
    private int id;
    private String username;
    private String password;

    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 getPassword() {
        return password;
    }

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

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

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5.UserMapper

package com.study.dao;

import com.study.domain.User;

import javax.jws.soap.SOAPBinding;
import java.util.List;

public interface UserMapper {
    public List<User> findAll();
    public User findById(int id);
     public List<User> findCondition(User user);
    public List<User> findBuIds(List<Integer> ids);
}

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6.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.study.dao.UserMapper">
    <!-- 查询-->
    <select id="findAll" resultType="user">
        select * from user
    </select>
    <!--根据id查询-->
    <select id="findById" parameterType="int" resultType="user">
        select * from user where id=#{id}
    </select>
     <!-- sql语句抽取-->
    <sql id="sqls"> select * from user</sql>
    <select id="findCondition" parameterType="user" resultType="user">
     <include refid="sqls"></include>
     <where>
         <if test="id!=0">
             and id=#{id}
         </if>
         <if test="username!=null">
             and username=#{username}
         </if>
         <if test="password!=null">
             and password=#{password}
         </if>
     </where>

    </select>
    <select id="findBuIds" parameterType="list" resultType="user">
        select * from user
        <where>
            <foreach collection="list" open="id in(" close=")" item="id" separator=",">
                #{id}
            </foreach>
        </where>
    </select>
</mapper>
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7.Test

package com.study.test;

import com.study.dao.UserMapper;
import com.study.domain.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 java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

public class Test {
    @org.junit.Test
    public void test1() throws IOException {
        User user = new User();
        user.setId(2);
        //user.setUsername("小飞侠");
       // user.setPassword("222222");
        InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> condition = mapper.findCondition(user);
        System.out.println(condition);  //[User{id=2, username='小飞侠', password='222222'}]

    }
    @org.junit.Test
    public void test2() throws IOException {
        List<Integer> list = new ArrayList<Integer>();
        list.add(1);
        list.add(2);
        list.add(3);
        InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> buIds = mapper.findBuIds(list);
        System.out.println(buIds);
        //[User{id=1, username='小马哥', password='111111'}, User{id=2, username='小飞侠', password='222222'},
        // User{id=3, username='马奎斯', password='333333'}]
    }


}

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