MyBatis基础：MyBatis数据基本操作（2）

1. MyBatis映射器

2. MyBatis数据基本操作

　　示例项目结构：

<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>libing</groupId>
    <artifactId>com-helloworld-api</artifactId>
    <packaging>war</packaging>
    <version>0.0.1-SNAPSHOT</version>
    <name>com-helloworld-api Maven Webapp</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.43</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.0-b07</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>
    <build>
        <finalName>com-helloworld-api</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.6.2</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

pom.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>
    <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/helloworld?characterEncoding=utf-8" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="mappers/RoleMapper.xml" />
    </mappers>
</configuration>

mybatis-config.xml

package com.libing.helloworld.model;

public class Role {

    private Integer id;

    private String roleName;

    public Integer getId() {
        return id;
    }

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

    public String getRoleName() {
        return roleName;
    }

    public void setRoleName(String roleName) {
        this.roleName = roleName;
    }

}

Role.java

<?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.libing.helloworld.dao.IRoleDao">
    <resultMap id="baseResultMap" type="com.libing.helloworld.model.Role">
        <id property="id" column="id" />
        <result property="roleName" column="role_name" />
    </resultMap>

    <select id="findAll" resultMap="baseResultMap">
        SELECT
            id,
            role_name
        FROM
            role
        ORDER BY id ASC
    </select>

    <select id="findBySearchText" resultMap="baseResultMap">
        SELECT
            id,
            role_name
        FROM
            role
        WHERE
            role_name LIKE CONCAT(CONCAT('%',#{searchText,jdbcType=VARCHAR}),'%')
        ORDER BY id ASC
    </select>

    <select id="findById" resultMap="baseResultMap">
        SELECT
            id,
            role_name
        FROM
            role
        WHERE id = #{id}
    </select>

    <insert id="insert" useGeneratedKeys="true" keyProperty="id" parameterType="com.libing.helloworld.model.Role">
        INSERT role
        (
            role_name
        )
        VALUES
        (
            #{roleName}
        )
    </insert>

    <update id="update" parameterType="com.libing.helloworld.model.Role">
        UPDATE role
        SET
            role_name=#{roleName}
        WHERE
            id = #{id}
    </update>

    <delete id="deleteById">
        DELETE FROM role
        WHERE
            id = #{id}
    </delete>

    <delete id="deleteByIds" parameterType="java.util.List">
        DELETE FROM role
        WHERE
            id IN
        <foreach collection="list" index="index" item="item" open="(" separator="," close=")">
            #{item}
        </foreach>
    </delete>
</mapper>

RoleMapper.xml

package com.libing.helloworld.test;

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

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

import com.libing.helloworld.dao.IRoleDao;
import com.libing.helloworld.model.Role;

public class RoleTest {
    SqlSession sqlSession = null;

    @Before
    public void init() {
        String resource = "mybatis-config.xml";
        InputStream inputStream = RoleTest.class.getClassLoader().getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        sqlSession = sqlSessionFactory.openSession();
    }

    @Test
    public void findAll() {
        try {
            IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);
            List<Role> roles = roleDao.findAll();

            Assert.assertNotNull(roles);
            Assert.assertTrue(roles.size() > 0);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
    }

    @Test
    public void findById() {
        try {
            IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);
            Role role = roleDao.findById(1);

            Assert.assertNotNull(role);
            Assert.assertNotNull(role.getRoleName());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
    }

    @Test
    public void insert() {
        try {
            IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

            Role role = new Role();
            role.setRoleName("测试");
            int result = roleDao.insert(role);

            // 只插入一条记录
            Assert.assertEquals(1, result);
            // id不为null
            Assert.assertNotNull(role.getId());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.rollback();
            sqlSession.close();
        }
    }

    public void Update() {
        try {
            IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

            Role role = roleDao.findById(1);
            Assert.assertNotNull(role);

            role.setRoleName("测试");
            int result = roleDao.update(role);

            // 只修改一条记录
            Assert.assertEquals(1, result);

            // 修改后的值
            Assert.assertEquals("测试", roleDao.findById(1).getRoleName());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.rollback();
            sqlSession.close();
        }
    }

    @Test
    public void deleteById() {
        try {
            IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

            Assert.assertNotNull(roleDao.findById(1));

            // 调用删除方法
            Assert.assertEquals(1, roleDao.deleteById(1));
            // 再次查询，判断是否为null
            Assert.assertNull(roleDao.findById(1));
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 由于sqlSessionFactory.openSession()是不自动提交的，不手动执行sqlSession.commit()不会提交到数据库
            sqlSession.rollback();
            sqlSession.close();
        }
    }

    @Test
    public void deleteByIds() {
        try {
            List<Integer> ids = new ArrayList<Integer>();
            ids.add(1);
            ids.add(2);

            IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);
            int result = roleDao.deleteByIds(ids);

            Assert.assertTrue(result > 0);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.rollback();
            sqlSession.close();
        }
    }
}

RoleTest.java

package com.libing.helloworld.dao;

import java.util.List;

import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Options;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.SelectKey;
import org.apache.ibatis.annotations.Update;

import com.libing.helloworld.model.Role;

public interface IRoleDao {

    @Select("SELECT id,role_name FROM role")
    @Results( value = {
        @Result(id = true, property = "id", column = "id"),
        @Result(property="roleName", column="role_name")
    })
    List<Role> findAll();

    @Select("SELECT id,role_name FROM role WHERE role_name LIKE CONCAT(CONCAT('%',#{searchText}),'%')")
    @Results( value = {
        @Result(id = true, property = "id", column = "id"),
        @Result(property="roleName", column="role_name")
    })
    List<Role> findBySearchText(@Param("searchText") String searchText);

    @Select("SELECT id,role_name FROM role WHERE id = #{id}")
    @Results( value = {
        @Result(id = true, property = "id", column = "id"),
        @Result(property="roleName", column="role_name")
    })
    Role findById(Integer id);

    @Insert({
        "INSERT INTO role(id,role_name)",
        " VALUES ",
        "(#{id}, #{roleName})"
    })
    @Options(useGeneratedKeys = true, keyProperty = "id")
    @SelectKey(statement="select last_insert_id()", keyProperty = "id", before = false, resultType = int.class)
    int insert(Role role);

    @Update({
        "UPDATE role SET ",
        "role_name = #{roleName} ",
        "WHERE id = #{id}"
    })
    int update(Role role);

    @Delete("DELETE FROM role WHERE id = #{id}")
    int deleteById(Integer id);

    int deleteByIds(List<Integer> ids);

}

IRoleDao.java

2.1 select

　　基于XML方式：

<resultMap id="baseResultMap" type="com.libing.helloworld.model.Role">
    <id property="id" column="id" />
    <result property="roleName" column="role_name" />
</resultMap>

<select id="findAll" resultMap="baseResultMap">
    SELECT
        id,
        role_name
    FROM
        role
    ORDER BY id ASC
</select>

　　基于注解方式：

@Select("SELECT id,role_name FROM role")
@Results( value = {
    @Result(id = true, property = "id", column = "id"),
    @Result(property="roleName", column="role_name")
})
List<Role> findAll();

　　单元测试：

@Test
public void findAll() {
    try {
        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);
        List<Role> roles = roleDao.findAll();

        Assert.assertNotNull(roles);
        Assert.assertTrue(roles.size() > 0);
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        sqlSession.close();
    }
}

　　XML中大于符号与小于符号转义：

　　>   >

　　<   &lt;

　　或使用 <![CDATA[   ]]>

<select id="findAll" resultMap="baseResultMap">
    SELECT
        id,
        role_name
    FROM
        role
    WHERE id &gt;= 10
    ORDER BY id ASC
</select>

<select id="findAll" resultMap="baseResultMap">
    SELECT
        id,
        role_name
    FROM
        role
    WHERE id <![CDATA[>=]]> 10
    ORDER BY id ASC
</select>

Role findById(Integer id);

<select id="findById" resultMap="baseResultMap">
    SELECT
        id,
        role_name
    FROM
        role
    WHERE
        id = #{id}
</select>

@Test
public void findById() {
    try {
        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);
        Role role = roleDao.findById(1);

        Assert.assertNotNull(role);
        Assert.assertNotNull(role.getRoleName());
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        sqlSession.close();
    }
}

@Select("SELECT id,role_name FROM role WHERE id = #{id}")
@Results( value = {
    @Result(id = true, property = "id", column = "id"),
    @Result(property="roleName", column="role_name")
})
Role findById(Integer id);

　　传递多个参数：

　　1>. 使用Map传递参数

List<Role> findByMap(Map<String, String> params);

<select id="findByMap" parameterType="map" resultMap="baseResultMap">
    SELECT
        id,
        role_name
    FROM
        role
    WHERE
        id != #{id}
    AND
        role_name = #{roleName}
</select>

@Test
public void findByMap() {
    try {
        Map<String, String> params = new HashMap<String, String>();
        params.put("id", "1");
        params.put("roleName", "管理员");
        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);
        List<Role> roles = roleDao.findByMap(params);

        Assert.assertNotNull(roles);
        Assert.assertTrue(roles.size() > 0);
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        sqlSession.close();
    }
}

　　2>. 使用注解方式传递参数

import org.apache.ibatis.annotations.Param;

List<Role> findByAnnotation(@Param("id") Integer id, @Param("roleName") String roleName);

<select id="findByAnnotation" resultMap="baseResultMap">
    SELECT
    　　id,
    　　role_name
    FROM
    　　role
    WHERE
    　　id != #{id}
    AND
    　　role_name = #{roleName}
</select>

　　3>. 使用JavaBean传递参数

package com.libing.helloworld.params;

public class RoleParam {

    private Integer id;

    private String roleName;

    public Integer getId() {
        return id;
    }

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

    public String getRoleName() {
        return roleName;
    }

    public void setRoleName(String roleName) {
        this.roleName = roleName;
    }

}

RoleParam.java

List<Role> findByRoleParam(RoleParam params);

<select id="findByRoleParam" parameterType="com.libing.helloworld.params.RoleParam" resultMap="baseResultMap">
    SELECT
        id,
        role_name
    FROM
        role
    WHERE
        id != #{id}
    AND
        role_name = #{roleName}
</select>

　　传递多个参数总结：

　　◊ 使用Map方式：Map扩展和维护困难，在实际应用中废弃这种传递参数方式。

　　◊ 使用@Param注解方式：参数个数<=5时是最佳的传参方式。

　　◊ JavaBean方式：当参数个数大于5个时，建议使用JavaBean方式。

2.2 insert

　　MyBatis在执行Insert语句之后返回一个整数，表示插入的记录数。

int insert(Role role);

<insert id="insert" useGeneratedKeys="true" keyProperty="id" parameterType="com.libing.helloworld.model.Role">
    INSERT role
    (
        role_name
    )
    VALUES
    (
        #{roleName}
    )
</insert>

　　其中，useGeneratedKeys：配置MyBatis使用JDBC的getGeneratedKeys()来获取由数据库内部生成的主键值，keyProperty：指定主键字段。

@Test
public void insert() {
    try {
        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

        Role role = new Role();
        role.setRoleName("测试");
        int result = roleDao.insert(role);

        // 只插入一条记录
        Assert.assertEquals(1, result);
        // id不为null
        Assert.assertNotNull(role.getId());
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        sqlSession.rollback();
        sqlSession.close();
    }
}

@Insert({
    "INSERT INTO role(id,role_name)",
    " VALUES ",
    "(#{id}, #{roleName})"
})
@Options(useGeneratedKeys = true, keyProperty = "id")
@SelectKey(statement="select last_insert_id()", keyProperty = "id", before = false, resultType = int.class)
int insert(Role role);

2.3 update

　　MyBatis在执行update语句之后返回一个整数，表示更新的记录数。

int update(Role role);

<update id="update" parameterType="com.libing.helloworld.model.Role">
    UPDATE role
    SET
        role_name = #{roleName}
    WHERE
        id = #{id}
</update>

@Test
public void Update() {
    try {
        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

        Role role = roleDao.findById(1);
        Assert.assertNotNull(role);

        role.setRoleName("测试");
        int result = roleDao.update(role);

        // 只修改一条记录
        Assert.assertEquals(1, result);

        // 修改后的值
        Assert.assertEquals("测试", roleDao.findById(1).getRoleName());
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        sqlSession.rollback();
        sqlSession.close();
    }
}

@Update({
    "UPDATE role SET ",
    "role_name = #{roleName} ",
    "WHERE id = #{id}"
})
int update(Role role);

2.4 delete

　　MyBatis在执行delete语句之后返回一个整数，表示删除的记录数。

int deleteById(Integer id);

<delete id="deleteById">
    DELETE FROM role
    WHERE
        id = #{id}
</delete>

@Test
public void deleteById() {
    try {
        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);

        Assert.assertNotNull(roleDao.findById(1));

        // 调用删除方法
        Assert.assertEquals(1, roleDao.deleteById(1));
        // 再次查询，判断是否为null
        Assert.assertNull(roleDao.findById(1));
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        // 由于sqlSessionFactory.openSession()是不自动提交的，不手动执行sqlSession.commit()不会提交到数据库
        sqlSession.rollback();
        sqlSession.close();
    }
}

@Delete("DELETE FROM role WHERE id = #{id}")
int deleteById(Integer id);

　　删除多条记录：

int deleteByIds(List<Integer> ids);

<delete id="deleteByIds" parameterType="java.util.List">
    DELETE FROM role
    WHERE
        id IN
    <foreach collection="list" index="index" item="item" open="("
        separator="," close=")">
        #{item}
    </foreach>
</delete>

@Test
public void deleteByIds() {
    try {
        List<Integer> ids = new ArrayList<Integer>();
        ids.add(1);
        ids.add(2);

        IRoleDao roleDao = sqlSession.getMapper(IRoleDao.class);
        int result = roleDao.deleteByIds(ids);

        Assert.assertTrue(result > 0);
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        sqlSession.rollback();
        sqlSession.close();
    }
}