Mybatis frame (IX): Mybatis use dynamic SQL

First, set up the environment

1, create a database table

Using data entry mybatis in: https://blog.csdn.net/yu1755128147/article/details/103358209

2, create a maven project and import coordinates

3, create entity classes, persistence dao interfaces

Entity class

package com.wedu.mybatis08.domain;

import java.io.Serializable;
import java.util.Date;

/**
 * 用户实体
 */
public class User implements Serializable {

    private Integer id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;

    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 Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

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

Persistence Layer Interface

package com.wedu.mybatis08.dao;

import java.util.List;

/**
 * 用户持久层接口
 */
public interface IUserDao {

}

 4. Create a database profile: jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test?useSSL=true&useUnicode=true&characterEncoding=utf8
jdbc.username=root
jdbc.password=123456

5, create a log file: log4j.properties

# Set root category priority to INFO and its only appender to CONSOLE.
#log4j.rootCategory=INFO, CONSOLE            debug   info   warn error fatal
log4j.rootCategory=debug, CONSOLE, LOGFILE

# Set the enterprise logger category to FATAL and its only appender to CONSOLE.
log4j.logger.org.apache.axis.enterprise=FATAL, CONSOLE

# CONSOLE is set to be a ConsoleAppender using a PatternLayout.
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n

# LOGFILE is set to be a File appender using a PatternLayout.
log4j.appender.LOGFILE=org.apache.log4j.FileAppender
log4j.appender.LOGFILE.File=E:\\project\\axis.log
log4j.appender.LOGFILE.Append=true
log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.LOGFILE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n

6, create a profile: SqlMapConfig.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>
    <!--引用外部的配置文件信息-->
    <properties resource="jdbc.properties"/>

    <!--配置别名-->
    <typeAliases>
        <package name="com.wedu.mybatis08.domain"/>
    </typeAliases>

    <!--配置环境-->
    <environments default="mysql">
        <environment id="mysql">
            <!--配置事务的类型-->
            <transactionManager type="JDBC"></transactionManager>
            <!--配置数据源-->
            <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>

    <!--配置映射文件的位置-->
    <mappers>
        <package name="com.wedu.mybatis08.dao" />
    </mappers>
</configuration>

7, create a mapping file: IUserDao.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.wedu.mybatis08.dao.IUserDao">
    <!--抽取重复的sql语句-->
    <sql id="findAllUser">
        select * from user
    </sql>
</mapper>

8, create a test class 

package com.wedu.mybatis08.dao;

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.After;
import org.junit.Before;

import java.io.IOException;

/**
 * mybatis的动态SQL测试
 */
public class UserDaoTest {

    private SqlSession session;
    private IUserDao userDao;

    @Before
    public void init() throws IOException {
        //1、加载配置文件并创建SqlSessionFactory工厂
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("SqlMapConfig.xml"));
        //2、使用工厂创建SqlSession对象
        session = factory.openSession();
        //3、使用SqlSession创建Dao接口的代理对象
        userDao = session.getMapper(IUserDao.class);
    }

    @After
    public void destroy(){
        //释放资源
        session.close();
    }
}

Second, the use of dynamic SQL

1, if the dynamic SQL elements

1.1, adding methods in IUserDao

    /**
     * 动态SQL...if...
     * @param user
     * @return
     */
    List<User> queryByIf(User user);

1.2, add dynamic sql in the IUserDao.xml

    <!--动态SQL...if...-->
    <select id="queryByIf" parameterType="user" resultType="user">
        <include refid="findAllUser"></include> where 1 = 1
        <if test="username != null">
          and username like #{username}
        </if>
    </select>

1.3, adding test method in a test class UserDaoTest

    /**
     * 测试动态SQl...if...
     */
    @Test
    public void testQueryByIf() {
        User user = new User();
        user.setUsername("%王%");
        List<User> users = userDao.queryByIf(user);
        for (User user1 : users) {
            System.out.println(user1);
        }
    }

2, choose the elements of dynamic SQL

2.1, adding methods in IUserDao

    /**
     * 动态SQL...choose...
     * @param user
     * @return
     */
    List<User> queryByChoose(User user);

2.2, add dynamic sql in the IUserDao.xml

    <!--动态SQL...choose...-->
    <select id="queryByChoose" parameterType="user" resultType="user">
        <include refid="findAllUser"></include> where 1 = 1
        <choose>
            <when test="username != null">
                and username like #{username}
            </when>
            <otherwise>
                order by username
            </otherwise>
        </choose>
    </select>

2.3, adding test method in a test class UserDaoTest

    /**
     * 测试动态SQl...choose...
     */
    @Test
    public void testQueryByChoose() {
        User user = new User();
        user.setUsername("%王%");
        List<User> users = userDao.queryByChoose(user);
        for (User user1 : users) {
            System.out.println(user1);
        }
    }

3, the trim elements in dynamic SQL

3.1, adding methods in IUserDao

    /**
     * 动态SQL...trim...
     * @param user
     * @return
     */
    List<User> queryByTrim(User user);

3.2, add dynamic sql in the IUserDao.xml

    <!--动态SQL...trim...-->
    <select id="queryByTrim" parameterType="user" resultType="user">
        <include refid="findAllUser"></include>
        <trim prefix="where" prefixOverrides="AND / OR">
            <if test="username != null">
                username like #{username}
            </if>
            <if test="sex != null">
                and sex = #{sex}
            </if>
        </trim>
    </select>

3.3, adding test method in a test class UserDaoTest

    /**
     * 测试动态SQl...trim...
     */
    @Test
    public void testQueryByTrim() {
        User user = new User();
        user.setUsername("%王%");
        List<User> users = userDao.queryByTrim(user);
        for (User user1 : users) {
            System.out.println(user1);
        }
    }

4, where elements of dynamic SQL

4.1, adding methods in IUserDao

    /**
     * 动态SQL...where...
     * @param user
     * @return
     */
    List<User> queryByWhere(User user);

4.2, add dynamic sql in the IUserDao.xml

    <!--动态SQL...where...-->
    <select id="queryByWhere" parameterType="user" resultType="user">
        <include refid="findAllUser"></include>
        <where>
            <if test="username != null">
                username like #{username}
            </if>
        </where>
    </select>

4.3, adding test method in a test class UserDaoTest

    /**
     * 测试动态SQl...where...
     */
    @Test
    public void testQueryByWhere() {
        User user = new User();
        user.setUsername("%王%");
        List<User> users = userDao.queryByWhere(user);
        for (User user1 : users) {
            System.out.println(user1);
        }
    }

5, the set of dynamic SQL operations

5.1, create value objects QueryVo

package com.wedu.mybatis08.domain;

import java.util.List;

public class QueryVo {

    private List<Integer> ids;

    public List<Integer> getIds() {
        return ids;
    }

    public void setIds(List<Integer> ids) {
        this.ids = ids;
    }
}

5.2, adding methods in IUserDao

    /**
     * 根据queryvo中提供的id集合，查询用户信息
     * @param queryVo
     * @return
     */
    List<User> findByQueryVo(QueryVo queryVo);

5.3, add dynamic sql in the IUserDao.xml

    <!--根据queryvo中提供的id集合，查询用户信息-->
    <select id="findByQueryVo" parameterType="user" resultType="user">
        <include refid="findAllUser"></include>
        <where>
            <if test="ids != null and ids.size()>0">
                <foreach collection="ids" open="and id in (" close=")" item="uid" separator=",">
                    #{uid}
                </foreach>
            </if>
        </where>
    </select>

5.4, ​​adding test method in a test class UserDaoTest

    /**
     * 根据queryvo中提供的id集合，查询用户信息
     */
    @Test
    public void testFindByQueryVo() {
        QueryVo queryVo = new QueryVo();
        List<Integer> list = new ArrayList<>();
        list.add(41);
        list.add(42);
        list.add(43);
        queryVo.setIds(list);
        List<User> users = userDao.findByQueryVo(queryVo);
        for (User user1 : users) {
            System.out.println(user1);
        }
    }