MyBatis的ResultMaps实战

àì夳堔傛蜴生んèń 2021-07-24 21:55 267阅读 0赞

**一 配置 **

1 db.properties

driver=com.mysql.jdbc.Driver
    url=jdbc:mysql://127.0.0.1:3306/mybatis
    username=root
    password=123456

2 log4j.xml

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">  
    <log4j:configuration  xmlns:log4j="http://jakarta.apache.org/log4j/">  
        <appender name="STDOUT"  class="org.apache.log4j.ConsoleAppender">  
            <layout class="org.apache.log4j.PatternLayout">  
                <param name="ConversionPattern" value="%5p [%t] %m%n"  />  
            </layout>  
        </appender>   
         <logger name="org.fkit.mapper.UserMapper">  
            <level value="DEBUG" />  
        </logger>
        <root>  
            <level value="ERROR" />  
            <appender-ref ref="STDOUT" />  
        </root>  
    </log4j:configuration>

3 mybatis-config.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>
         
         <properties resource="db.properties"/>
         
         <settings>
               <setting name="logImpl" value="LOG4J"/>
         </settings>
         <environments default="mysql">
         
        <environment id="mysql">
        
          <transactionManager type="JDBC"/>
          
          <dataSource type="POOLED">
            <property name="driver" value="${driver}"/>
            <property name="url" value="${url}"/>
            <property name="username" value="${username}"/>
            <property name="password" value="${password}"/>
          </dataSource>
        </environment>
      </environments>
      
      <mappers>
          <mapper resource="org/fkit/mapper/UserMapper.xml"/>
      </mappers>
    </configuration>

**二 领域模型**

1 User

package org.fkit.domain;
    import java.io.Serializable;
    /**
    
    *
    * CREATE TABLE `tb_user` (
      `id` INT(11) NOT NULL AUTO_INCREMENT,
      `name` VARCHAR(18) DEFAULT NULL,
      `sex` CHAR(2) DEFAULT NULL,
      `age` INT(11) DEFAULT NULL,
      PRIMARY KEY  (`id`)
    )
    */
    public class User implements Serializable{
         
         private static final long serialVersionUID = 1L;
         
         private Integer id;
         private String name;
         private String sex;
         private Integer age;
         
         public User() {
               super();
               // TODO Auto-generated constructor stub
         }
         
         public User( String name, String sex, Integer age) {
               super();
               this.name = name;
               this.sex = sex;
               this.age = age;
         }
         public Integer getId() {
               return id;
         }
         public void setId(Integer id) {
               this.id = id;
         }
         public String getName() {
               return name;
         }
         public void setName(String name) {
               this.name = name;
         }
         public String getSex() {
               return sex;
         }
         public void setSex(String sex) {
               this.sex = sex;
         }
         public Integer getAge() {
               return age;
         }
         public void setAge(Integer age) {
               this.age = age;
         }
         @Override
         public String toString() {
               return "User [id=" + id + ", name=" + name + ", sex="  + sex + ", age="
                         + age + "]";
         }
    }

2 Student

package org.fkit.domain;
    import java.io.Serializable;
    public class Student implements Serializable{
         
         private static final long serialVersionUID = 1L;
         
         private Integer id;
         private String name;
         private String sex;
         private Integer age;
         // 关联的Clazz对象
         private Clazz clazz;
         public Student() {
               super();
               // TODO Auto-generated constructor stub
         }
         public Integer getId() {
               return id;
         }
         public void setId(Integer id) {
               this.id = id;
         }
         public String getName() {
               return name;
         }
         public void setName(String name) {
               this.name = name;
         }
         public String getSex() {
               return sex;
         }
         public void setSex(String sex) {
               this.sex = sex;
         }
         public Integer getAge() {
               return age;
         }
         public void setAge(Integer age) {
               this.age = age;
         }
         public Clazz getClazz() {
               return clazz;
         }
         public void setClazz(Clazz clazz) {
               this.clazz = clazz;
         }
         @Override
         public String toString() {
               return "Student [id=" + id + ", name=" + name + ",  sex=" + sex
                         + ", age=" + age + ", clazz=" + clazz +  "]";
         }
         
         
    }

3 Clazz

package org.fkit.domain;
    
    import java.io.Serializable;
    import java.util.List;
    
    public class Clazz implements Serializable{
        
        private static final long serialVersionUID = 1L;
        
        private Integer id;
        private String code;
        private List<Student> students;
        public Clazz() {
            super();
            // TODO Auto-generated constructor stub
        }
        public Integer getId() {
            return id;
        }
        public void setId(Integer id) {
            this.id = id;
        }
        public String getCode() {
            return code;
        }
        public void setCode(String code) {
            this.code = code;
        }
        public List<Student> getStudents() {
            return students;
        }
        public void setStudents(List<Student> students) {
            this.students = students;
        }
        @Override
        public String toString() {
            return "Clazz [id=" + id + ", code=" + code + "]";
        }
        
    
    }

**三 会话工厂**

package org.fkit.factory;
    
    import java.io.InputStream;
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    public class FKSqlSessionFactory {
        
        private static SqlSessionFactory sqlSessionFactory = null;
        
        // 初始化创建SqlSessionFactory对象
        static{
            try (// 读取mybatis-config.xml文件
                    InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
                ){
                sqlSessionFactory = new SqlSessionFactoryBuilder()
                        .build(is);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        
        // 获取SqlSession对象的静态方法
        public static SqlSession getSqlSession(){
            return sqlSessionFactory.openSession();
        }
    
        // 获取SqlSessionFactory的静态方法
        public static SqlSessionFactory getSqlSessionFactory() {
            return sqlSessionFactory;
        }
    
    }

**四 mapper**

<?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.fkit.mapper.UserMapper">
      
      <select id="selectUser" resultType="map">
          SELECT * FROM TB_USER
      </select>
      <resultMap id="userResultMap" type="org.fkit.domain.User">
           <id property="id" column="user_id" />
           <result property="name" column="user_name"/>
           <result property="sex" column="user_sex"/>
           <result property="age" column="user_age"/>
         </resultMap>
      
       <select id="selectUser2" resultMap="userResultMap">
          SELECT * FROM TB_USER2
      </select>
      
      
      
      <resultMap id="studentResultMap"  type="org.fkit.domain.Student">
           <id property="id" column="id" />
           <result property="name" column="name"/>
           <result property="sex" column="sex"/>
           <result property="age" column="age"/>
           
           <association property="clazz" column="clazz_id"
           javaType="org.fkit.domain.Clazz"
           select="selectClazzWithId"/>
         </resultMap>
         
      
      <select id="selectClazzWithId"  resultType="org.fkit.domain.Clazz">
          SELECT * FROM TB_CLAZZ where id = #{id}
      </select>
      
      
      <select id="selectStudent" resultMap="studentResultMap">
          SELECT * FROM TB_STUDENT
      </select>
      
      
      <resultMap id="clazzResultMap" type="org.fkit.domain.Clazz">
           <id property="id" column="id" />
           <result property="code" column="code"/>
           
           <collection property="students" javaType="ArrayList"
           column="id" ofType="org.fkit.domain.Student"
           select="selectStudentWithId"/>
         </resultMap>
         
         
         <select id="selectStudentWithId"  resultType="org.fkit.domain.Student">
               SELECT * FROM TB_STUDENT where clazz_id = #{id}
          </select>
          
         
      <select id="selectClazz" resultMap="clazzResultMap">
          SELECT * FROM TB_CLAZZ
      </select>
      
    </mapper>

**五 测试**

1 SelectMapTest

package org.fkit.test;
    
    import java.util.List;
    import java.util.Map;
    import org.apache.ibatis.session.SqlSession;
    import org.fkit.factory.FKSqlSessionFactory;
    
    public class SelectMapTest {
    
        public static void main(String[] args) {
            // 定义SqlSession变量
            SqlSession sqlSession = null;
            try {
                // 创建SqlSession实例
                sqlSession = FKSqlSessionFactory.getSqlSession();
                // 查询TB_USER表所有数据返回List集合,集合中的每个元素都是一个Map
                List<Map<String,Object>> list
                    = sqlSession.selectList("org.fkit.mapper.UserMapper.selectUser");
                // 遍历List集合，打印每一个Map对象
                list.forEach(row -> System.out.println(row));
                // 提交事务
                sqlSession.commit();
            } catch (Exception e) {
                // 回滚事务
                sqlSession.rollback();
                e.printStackTrace();
            }finally {
                // 关闭SqlSession
                if(sqlSession != null)
                    sqlSession.close();
            }
        }
    }

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2 ResultMapTest

package org.fkit.test;
    
    import java.util.List;
    import org.apache.ibatis.session.SqlSession;
    import org.fkit.domain.User;
    import org.fkit.factory.FKSqlSessionFactory;
    
    public class ResultMapTest {
    
        public static void main(String[] args) {
            // 定义SqlSession变量
            SqlSession sqlSession = null;
            try {
                // 创建SqlSession实例
                sqlSession = FKSqlSessionFactory.getSqlSession();
                // 查询TB_USER表所有数据返回List集合,集合中的每个元素都是一个Map
                List<User> user_list
                    = sqlSession.selectList("org.fkit.mapper.UserMapper.selectUser2");
                // 遍历List集合，打印每一个Map对象
                user_list.forEach(user -> System.out.println(user));
                // 提交事务
                sqlSession.commit();
            } catch (Exception e) {
                // 回滚事务
                sqlSession.rollback();
                e.printStackTrace();
            }finally {
                // 关闭SqlSession
                if(sqlSession != null)
                    sqlSession.close();
            }
        }
    }

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3 SelectClazzTest

package org.fkit.test;
    
    import java.util.List;
    import org.apache.ibatis.session.SqlSession;
    import org.fkit.domain.Clazz;
    import org.fkit.domain.Student;
    import org.fkit.factory.FKSqlSessionFactory;
    
    public class SelectClazzTest {
    
        public static void main(String[] args)  {
            // 定义SqlSession变量
            SqlSession sqlSession = null;
            try {
                // 创建SqlSession实例
                sqlSession = FKSqlSessionFactory.getSqlSession();
                // 查询TB_CLAZZ表所有数据返回List集合,集合中的每个元素都是一个Clazz对象
                List<Clazz> clazz_list
                    = sqlSession.selectList("org.fkit.mapper.UserMapper.selectClazz");
                // 遍历List集合，打印每一个Clazz对象和该Clazz关联的所有Student对象
                for(Clazz clazz : clazz_list){
                    System.out.println(clazz);
                    List<Student> student_list = clazz.getStudents();
                    for(Student stu : student_list){
                        System.out.println(stu.getId() + " " + stu.getName() + " " + stu.getSex() + " " + stu.getAge());
                    }
                }
                // 提交事务
                sqlSession.commit();
            } catch (Exception e) {
                // 回滚事务
                sqlSession.rollback();
                e.printStackTrace();
            }finally {
                // 关闭SqlSession
                if(sqlSession != null)
                    sqlSession.close();
            }
        
        }
    }

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4 SelectStudentTest

package org.fkit.test;
    
    import java.util.List;
    import org.apache.ibatis.session.SqlSession;
    import org.fkit.domain.Student;
    import org.fkit.factory.FKSqlSessionFactory;
    
    public class SelectStudentTest {
    
        public static void main(String[] args)  {
            // 定义SqlSession变量
            SqlSession sqlSession = null;
            try {
                // 创建SqlSession实例
                sqlSession = FKSqlSessionFactory.getSqlSession();
                // 查询TB_USER表所有数据返回List集合,集合中的每个元素都是一个Student对象
                List<Student> student_list
                    = sqlSession.selectList("org.fkit.mapper.UserMapper.selectStudent");
                // 遍历List集合，打印每一个Student对象，该对象包含关联的Clazz对象
                student_list.forEach(stu -> System.out.println(stu));
                // 提交事务
                sqlSession.commit();
            } catch (Exception e) {
                // 回滚事务
                sqlSession.rollback();
                e.printStackTrace();
            }finally {
                // 关闭SqlSession
                if(sqlSession != null)
                    sqlSession.close();
            }
        }
    }

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