An example of resultMap and resultType for getting started with Mybatis

An example of resultMap
and resultType for getting started with
Mybatis In the case of entity classes resultType: suitable for use The return value data type is non-custom, that is, the type provided by jdk resultMap: the unique identifier of the data type of the mapped entity class resultMap column: the field name of the library table property: the attribute name in the entity class Configuration map file: <?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"> <!-- namespace: The namespace of the current library table mapping file, the only one cannot be repeated --> <mapper namespace="com.hao947.sql.mapper.PersonMapper">   <!-- type: The data type id of the mapped entity class: the unique identifier of the resultMap -->
























  <resultMap type="person" id="BaseResultMap">
    <!-- column: the field name of the library table property: the attribute name in the entity class-->
    <id column="person_id" property="personId" />
    < result column="name" property="name" />
    <result column="gender" property="gender" />
    <result column="person_addr" property="personAddr" />
    <result column="birthday" property= "birthday" />
  </resultMap>
  <!--id: the unique identifier of the current sql
     parameterType: the data type of the input parameter
     resultType: the data type of the return value
     #{}: used to accept parameters, if a parameter is passed# The content of {id} is arbitrary. If there are multiple parameters, there are certain rules. The precompiled form is selected
    * from person p where p. id = ? , high security -->

  <!-- The return value type of the sql statement uses resultMap -->
  <select id="selectPersonById" parameterType="java.lang.Integer"
    resultMap="BaseResultMap">
    select * from person p where p.person_id = #{id}
  </select>
  <!-- resultMap: suitable for use when the return value is a custom entity class
  resultType: suitable data type for the return value It is non-customized, that is, the type provided by jdk-->
  <select id="selectPersonCount" resultType="java.lang.Integer">
    select count(*) from
    person
  </select>

  <select id="selectPersonByIdWithMap" parameterType ="java.lang.Integer"
    resultType="java.util.Map">
    select * from person p where p.person_id= #{id}
    </select>

</mapper>
Entity class Person.java

<pre name=" code" class="java">package com.hao947. model;
import java.util.Date;
public class Person {
  private Integer personId;
  private String name;
  private Integer gender;
  private String personAddr;
  private Date birthday;
  @Override
  public String toString() {
    return "Person [personId=" + personId + ", name=" + name + ", gender="
        + gender + ", personAddr=" + personAddr + ", birthday="
        + birthday + "]";
  }
}
测试类

public class PersonTest {
  SqlSessionFactory sqlSessionFactory;
  @Before
  public void setUp() throws Exception {
    // 读取资源流
    InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
    // Initialize session factory
    sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
  }

 

  @Test
  public void selectPersonById() {
    // 创建一个sqlsession
    SqlSession session = sqlSessionFactory.openSession();
    try {
      Person p = session.selectOne(
          "com.hao947.sql.mapper.PersonMapper.selectPersonById", 1);
      System.out.println(p);
    } finally {
      session.close();
    }
  }
  @Test
  public void selectPersonCount() {
    // 创建一个sqlsession
    SqlSession session = sqlSessionFactory.openSession();
    try {
      Integer p = session.selectOne(
          "com.hao947.sql.mapper.PersonMapper.selectPersonCount");
      System.out.println(p);
    } finally {
      session.close();
    }
  }
  @Test
  public void selectPersonByIdWithMap() {
    // 创建一个sqlsession
    SqlSession session = sqlSessionFactory.openSession();
    try {
      Map<String ,Object> map = session.selectOne(
          "com.hao947.sql.mapper.PersonMapper.selectPersonByIdWithMap",1);
      System.out.println(map);
    } finally {
      session.close();
    }
  }
}