Mybatis（5）：使用sql映射文件，将返回结果封装为ResulMap

四部曲：

1.写接口  +  2.写映射sql  + 3.把mapper注册到mybatis的配置文件  + 4.写单元测试和运行

      今天通过使用Mybatis框架·，将MySQL查询得到的数据封装为ResulMap，并映射到实体类User.java。这个过程是通过设置<select ></select >的resultMap属性为<resultMap></resultMap>的id，从而调用了它。

下面是具体的代码：

（1）首先新建一个User.java文件，作为这次的实体类，注意一定要有setter方法（mybatis通过setter访问器进行读取）：

package com.smbms.entities;import java.util.Date;import java.util.List;public class User {private Integer id;private String userCode;private String userName;private String userPassword;private Integer gender;private Date birthday;private String phone;private String address ;private Integer userRole;private Integer createdBy;private Date creationDate;private Integer modifyBy;private Date modifyDate;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getUserCode() {return userCode;}public void setUserCode(String userCode) {this.userCode = userCode;}public String getUserName() {return userName;}public void setUserName(String userName) {this.userName = userName;}public String getUserPassword() {return userPassword;}public void setUserPassword(String userPassword) {this.userPassword = userPassword;}public Integer getGender() {return gender;}public void setGender(Integer gender) {this.gender = gender;}public Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}public String getPhone() {return phone;}public void setPhone(String phone) {this.phone = phone;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}public Integer getUserRole() {return userRole;}public void setUserRole(Integer userRole) {this.userRole = userRole;}public Integer getCreatedBy() {return createdBy;}public void setCreatedBy(Integer createdBy) {this.createdBy = createdBy;}public Date getCreationDate() {return creationDate;}public void setCreationDate(Date creationDate) {this.creationDate = creationDate;}public Integer getModifyBy() {return modifyBy;}public void setModifyBy(Integer modifyBy) {this.modifyBy = modifyBy;}public Date getModifyDate() {return modifyDate;}public void setModifyDate(Date modifyDate) {this.modifyDate = modifyDate;}public User(Integer id, String userCode, String userName, String userPassword, Integer gender, Date birthday,String phone, String address, Integer userRole, Integer createdBy, Date creationDate, Integer modifyBy,Date modifyDate) {super();this.id = id;this.userCode = userCode;this.userName = userName;this.userPassword = userPassword;this.gender = gender;this.birthday = birthday;this.phone = phone;this.address = address;this.userRole = userRole;this.createdBy = createdBy;this.creationDate = creationDate;this.modifyBy = modifyBy;this.modifyDate = modifyDate;}public User() {super();// TODO 自动生成的构造函数存根}@Overridepublic String toString() {return "User [id=" + id + ", userCode=" + userCode + ", userName=" + userName + ", userPassword=" + userPassword+ ", gender=" + gender + ", birthday=" + birthday + ", phone=" + phone + ", address=" + address+ ", userRole=" + userRole + ", createdBy=" + createdBy + ", creationDate=" + creationDate+ ", modifyBy=" + modifyBy + ", modifyDate=" + modifyDate + "]";}}

（2）然后，新建一个接口类 UserMapper.java，定义一个新的方法 public List<User> getUserList(User user) ;：

package com.smbms.dao;import java.util.List;import java.util.Map;import org.apache.ibatis.annotations.Param;import com.smbms.entities.User;public interface UserMapper {public List<User> getUserList(User user);}

（3）然后，新建一个UserMapper.xml文件，用来编写sql映射语句：

【业务模型传递参数到sql执行查询操作：parameterType = "com.smbms.entities.User“；】

【数据库返回的结果到业务模型，调用了 resultMap：resultMap="userlist" 】

<?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.smbms.dao.UserMapper">       <select id="getUserList" resultMap="userlist" parameterType="com.smbms.entities.User">select u.*,r.rolename from  smbms_user u ,smbms_role r    where u.username like CONCAT('%',#{username},'%')      and u.userRole = #{userRole} and u.userRole = r.id</select><resultMap type="com.smbms.entities.User" id="userlist"><result property="id" column="id"/><result property="userCode" column="userCode"/><result property="userName" column="username"/><result property="phone" column="phone"/><result property="birthday" column="birthday"/><result property="gender" column="gender"/><result property="userRole" column="userRole"/><result property="userRoleName" column="userRoleName"/></resultMap> </mapper> 

（4）编写测试用例，导入JUnit4.jar后，可以新建测试用例UserTest.java：

package com.smbms.entities;import java.io.IOException;import java.io.InputStream;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.ArrayList;import java.util.Date;import java.util.HashMap;import java.util.List;import java.util.Map;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.Test;import com.smbms.dao.ProviderMapper;import com.smbms.dao.UserMapper;public class UserTest {public SqlSession getSqlSession() throws IOException{String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory build = new SqlSessionFactoryBuilder().build(inputStream);SqlSession openSession = build.openSession();return openSession;}

//使用resultMap完成查询结果的展现@Testpublic void test06() throws IOException{User user = new User();user.setUserName("mmb");user.setUserRole(110);SqlSession session = getSqlSession();UserMapper mapper = session.getMapper(UserMapper.class);List<User> userByUsername = mapper.getUserList(user);for(User user1:userByUsername){System.out.println("+*+:" +user1.getUserRoleName()+user1.getPhone()+user1.getUserCode()+user1.getUserName()+user1.getUserRole());}}

}

由此完成一个小Demo。

注意之处：

（1）ResulMap 具有两个元素：type 和 id ，type对应结果映射的实体类，id 是Map的唯一标识；

（2）result 是 ResulMap 下的标签元素，具有两个属性：property 和 column， column 对应于数据库的列名，property 对应于实体类定义的属性变量。