MyBatis的使用步骤及配置

1.导入mybatis的jar包：mybatis-x.x.x.jar

2.使用XML配置mybatis，创建SqlSessionFactory

　　XML配置文件的名称通常为mybatis-config.xml,内容基本格式如下：

<?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="oracle.jdbc.driver.OracleDriver"/>
        <property name="url" value="jdbc:oracle:thin:@127.0.0.1:1521:orcl"/>
        <property name="username" value="username"/>
        <property name="password" value="password"/>
      </dataSource>
    </environment>
  </environments>
  <mappers>
    <mapper resource="org/mybatis/example/BlogMapper.xml"/>
    <!-- <package name="com.example.manager.mapper"/> -->
  </mappers>
</configuration>

该配置文件使用文件流的形式读入，通过mybatis的工具类Resources加载资源文件：

String resource = "org/mybatis/example/mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

3.从 SqlSessionFactory 中获取 SqlSession

SqlSession session = sqlSessionFactory.openSession();
try {
  Blog blog = (Blog) session.selectOne("org.mybatis.example.BlogMapper.selectBlog", 101);
} finally {
  session.close();
}

4.最简单的使用方法：mybatis-config.xml + mapper.xml + test.java

mybatis-config.xml配置

<mapper resource="org/mybatis/example/BlogMapper.xml"/>

resource的路径通常为包路径，众多mapper.xml通常被放置在一个包下

mapper.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="org.mybatis.example.BlogMapper">
  <select id="selectBlog" resultType="Map">
    select * from Blog where id = #{id}
  </select>
</mapper>

namespace：命名空间，映射查询的关键参数
id：调用方法定义
resultType：结果集对象类型（Map可以被HashMap接收，然后转为json，也可以自定义类型）
传递参数：参数替换分两种：#{id} => 预处理语句的？ || '${id}' => 直接替换为变量

test.java

public static void main(String[] args) {
    SqlSessionFactory sqlSessionFactory;
    SqlSession session = null;
    try {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        session = sqlSessionFactory.openSession();
        HashMap<String,String> result = session.selectOne("selectBlog", 110);
        System.out.println("Result: "+result);
    } catch (Exception ex) {
        ex.printStackTrace();
    } finally {
        if(session != null){
            session.close();
        }
    }
}

session.selectOne是session自带方法（selectList可以获取多条数据），传入的第一个字符串就是之前定义的id，第二个参数是传入的参数(多个参数可以使用一个HashMap来传参)。

5.简单抽象方法：mybatis-config.xml + mapper.xml + interface.java + test.java

mybatis-config.xml

<package name="com.mybatis.manager.mapper"/>

mapper.xml

<mapper namespace="com.mybatis.manager.mapper.ReleaseDTOMapper">
<select id="getReleaseNote" parameterType="map" resultType="map">
SELECT rn.* FROM GPCM_RELEASE_NOTE rn where rn.state = #{STATE} and rn.upgrade_id = #{UPGRADE_ID}
</select>
<select id="getUpgradeNote" parameterType="map" resultType="map">
SELECT un.* FROM GPCM_UPGRADE_NOTE un
</select>
</mapper>

interface.java

public interface ReleaseDTOMapper {    
    public HashMap<String,String> getReleaseNote(HashMap<String,String> param);
    
    public ArrayList<HashMap<String,String>> getUpgradeNote();
}

test.java

public static void main(String[] args) {
    SqlSessionFactory sqlSessionFactory;
    SqlSession session = null;
    try {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        session = sqlSessionFactory.openSession();
        ReleaseDTOMapper mapper = session.getMapper(ReleaseDTOMapper.class);
        
        HashMap<String,String> param = new HashMap<String,String>();
        param.put("STATE", "N");
        param.put("UPGRADE_ID","2");
        HashMap<String,String> result = mapper.getReleaseNote(param);
        System.out.println("Result: "+result);
        List<HashMap<String,String>> rs = mapper.getUpgradeNote();
        for(HashMap<String,String> r : rs){
            System.out.println("Result: "+r);
        }            
    } catch (Exception ex) {
        ex.printStackTrace();
    } finally {
        if(session != null){
            session.close();
        }
    }
}

6.通用方法：使用自定义数据类型映射参数和结果集

mapper.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.mybatis.manager.mapper.ReleaseDTOMapper">
  <resultMap id="BaseResultMap" type="com.mybatis.manager.persist.ReleaseNoteDTO" >
    <result column="RELEASE_ID" property="releaseId" jdbcType="INTEGER" />
    <result column="RELEASE_NAME" property="releaseName" jdbcType="VARCHAR" />
    <result column="RELEASE_DESC" property="releaseDesc" jdbcType="VARCHAR" />
    <result column="UPGRADE_ID" property="upgradeId" jdbcType="INTEGER" />
    <result column="STATE" property="state" jdbcType="VARCHAR" />
    <result column="CREATE_DATE" property="createDate" jdbcType="TIMESTAMP" />
    <result column="MOD_DATE" property="modDate" jdbcType="TIMESTAMP" />
    <result column="UPGRADE_DATE" property="upgradeDate" jdbcType="TIMESTAMP" />
    </resultMap>
  <select id="getReleaseNote" parameterType="com.mybatis.manager.persist.ReleaseNoteDTO" resultMap="BaseResultMap">
    SELECT rn.* FROM GPCM_RELEASE_NOTE rn where rn.state = #{state,jdbcType=VARCHAR} and rn.upgrade_id = #{upgradeId,jdbcType=INTEGER}
  </select>
</mapper>

注意resultType -> resultMap，列与java对象的参数必需要对应，否则获取的结果就是null。

　　传入的参数为一个是可以定义parameterType="java.lang.Integer"，多个参数必需合为一个对象传输，如Map或自定义Dto。

　　可以使用多表查询，将结果集传入一个自定义Dto中，结果集绑定如下：

<resultMap id = "Upgrade" type="com.mybatis.manager.persist.UpgradeNoteDto">
    <result column="UPGRADE_ID" property="upgradeId" jdbcType="INTEGER" />
    <result column="UPGRADE_NAME" property="upgradeName" jdbcType="VARCHAR" />
</resultMap>
<resultMap id="BaseResultMap" type="com.mybatis.manager.persist.ReleaseNoteDto" >
    <result column="RELEASE_ID" property="releaseId" jdbcType="INTEGER" />
    <result column="RELEASE_NAME" property="releaseName" jdbcType="VARCHAR" />
    <result column="RELEASE_DESC" property="releaseDesc" jdbcType="VARCHAR" />
    <association property = "upgrade" javaType="com.mybatis.manager.persist.UpgradeNoteDto" resultMap = "Upgrade"/>
</resultMap>

property = "upgrade"在Dto中定义为

private UpgradeNoteDto upgrade;

ReleaseNoteDTO.java 自定义数据模型

public class ReleaseNoteDTO {
    private Integer releaseId;
    private String releaseName;
    private String releaseDesc;
    private Integer upgradeId;
    private String state;
    private Date createDate;
    private Date modDate;
    private Date upgradeDate;
    /*******************
    *GETTER/SETTER
    *******************/
}

interface.java

public interface ReleaseNoteDtoMapper {    
    public ReleaseNoteDto getReleaseNote(ReleaseNoteDto param);    
}

test.java

ReleaseNoteDTO param = new ReleaseNoteDTO();
param.setState("N");
param.setUpgradeId(2);
ReleaseNoteDTO result = mapper.getReleaseNote(param);
System.out.println("Result: "+result.getReleaseDesc());

7.基本应用的结构参考

原文出处：https://www.cnblogs.com/windyofsky/p/5230570.html