MyBatis关联关系配置

db.properties配置文件 db.name=root db.password=123456 db.url=jdbc\:mysql\://localhost\:3306/test db.driver=com.mysql.jdbc.Driver configuration.xml配置文件 !DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <properties resource="db.properties"/> <!-- 给实体 取别名 --> <typeAliases> <typeAlias type="com.mybatis.entity.ClassInfo" alias="classInfo"/> <typeAlias type="com.mybatis.entity.StudentInfo" alias="studentInfo"/> </typeAliases> <environments default="en"> <environment id="en"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="${db.driver}"/> <property name="url" value="${db.url}"/> <property name="username" value="${db.name}"/> <property name="password" value="${db.password}"/> </dataSource> </environment> </environments> <!-- 映射配置文件 --> <mappers> <mapper resource="com/mybatis/entity/classInfo.xml"/> <mapper resource="com/mybatis/entity/studentInfo.xml"/> </mappers> </configuration> studentinfo.xml映射配置文件信息： <?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"> <!-- com.mybatis.entity.StudentInfo --> <mapper namespace="com.mybatis.entity.*"> <resultMap type="com.mybatis.entity.StudentInfo" id="stu"> <result property="id" column="id"/> <result property="name" column="name"/> <result property="age" column="age"/> <result property="sex" column="sex"/> <result property="classid" column="classid"/> <!-- 一对多的配置 --> <association property="cs" javaType="com.mybatis.entity.ClassInfo" resultMap="class" /> </resultMap> <!-- 查询所有 --> <select id="queryAll" resultMap="stu"> select * from studentinfo a,classinfo b where a.classid=b.classid </select> </mapper> classinfo.xml映射配置 文件信息： <?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.entity.*"> <resultMap type="com.mybatis.entity.ClassInfo" id="class"> <result property="classid" column="classid"/> <result property="classname" column="classname"/> <!-- 多对一的配置 --> <collection property="stu" ofType="com.mybatis.entity.StudentInfo" resultMap="stu"/> </resultMap> <!-- 查询 --> <select id="queryCs" parameterType="int" resultMap="class"> select * from studentinfo a, classinfo b where a.classid=b.classid and a.classid=#{classid} </select> </mapper> 实体类studentInfo package com.mybatis.entity; public class StudentInfo { private int id; private String name; private int age; private String sex; private int classid; private ClassInfo cs; public StudentInfo(){} public StudentInfo(int id, String name, int age, String sex, int classid, ClassInfo cs) { super(); this.id = id; this.name = name; this.age = age; this.sex = sex; this.classid = classid; this.cs = cs; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public String getSex() { return sex; }
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public void setSex(String sex) { this.sex = sex; } public int getClassid() { return classid; } public void setClassid(int classid) { this.classid = classid; } public ClassInfo getCs() { return cs; } public void setCs(ClassInfo cs) { this.cs = cs; } } classInfo实体类 package com.mybatis.entity;
import java.util.List; import java.util.Set; public class ClassInfo { private int classid; private String classname; private List<StudentInfo> stu; public ClassInfo(){} public ClassInfo(int classid, String classname, List<StudentInfo> stu) { super(); this.classid = classid; this.classname = classname; this.stu = stu; } public int getClassid() { return classid; } public void setClassid(int classid) { this.classid = classid; } public String getClassname() { return classname; } public void setClassname(String classname) { this.classname = classname; } public List<StudentInfo> getStu() { return stu; } public void setStu(List<StudentInfo> stu) { this.stu = stu; } }

测试： /** * * 只用于测试 * @author Administrator * */ public class StudentInfoDAO implements IStudentInfoDAO { public static SqlSession getSession(){ Reader red=null; try { //读取配置文件 red=Resources.getResourceAsReader("configuration.xml"); //获取一个sqlsessionfactory SqlSessionFactory fc=new SqlSessionFactoryBuilder().build(red); //获取sqlsession return fc.openSession(); } catch (Exception e) { e.printStackTrace(); } return null; } //关闭session public static void closeSession(SqlSession session){ session.close(); } //查询学生 public List<StudentInfo> queryAll() { SqlSession session=StudentInfoDAO.getSession(); //查询所有 List<StudentInfo> list=session.selectList("queryAll"); //关闭session StudentInfoDAO.closeSession(session); return list; } //根据班级id查询学生信息 public List<ClassInfo> queryCs(){ SqlSession session=StudentInfoDAO.getSession(); //查询所有 List<ClassInfo> list=session.selectList("queryCs",1); //关闭session StudentInfoDAO.closeSession(session); return list; } public static void main(String[] args) { StudentInfoDAO dao=new StudentInfoDAO(); // List<StudentInfo> list=dao.queryAll(); // for(StudentInfo stu:list){ // System.out.println("学生："+stu.getName()+">>>>>>班级:"+stu.getCs().getClassname()); // } List<ClassInfo> list=dao.queryCs(); for(int i=0;i<list.size();i++){ System.out.println(list.get(i).getClassid()); for(int j=0;j<list.get(i).getStu().size();j++){ System.out.println(list.get(i).getStu().get(j).getName()); } } } }