Mybatis的基本使用方法

港控/mmm° 2022-05-25 14:07 245阅读 0赞

**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"/>
        
      </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

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

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

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

![787723-20160301165649595-68636191.png][]

附录：相关参考资料

官网中文教程 http://www.mybatis.org/mybatis-3/zh/getting-started.html

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[787723-20160301165649595-68636191.png]: /images/20220525/598f420f6618484792adff7823dde3eb.png
[70]: /images/20220525/8b914811da6f418d879c2d2aeed6c776.png