7
- column 表示当前查询数据库表的列名DEPARTMENT_ID
- property 表示返回类型PhoneUserIdAndDepartment属性名department
- javaType 表示该属性对于的类型名称，本例是一个ArrayList集合
- select 表示执行的查询语句，将查询到的数据封装到property所代表的类型对象当中
- ofType 表示集合当中的类型
7.1 基本应用
7.1.1 java bean
- 同 6.1.1
7.1.2 映射文件
7.1.3 测试代码
SqlSession session = SqlSessionFactoryUtil.getSession();
List classes = session.selectList("com.zhougl.web.dao.WebClassDao.selectClass");
classes.forEach(classe ->{
System.out.println(classe);
List students = classe.getStudents();
students.forEach(student -> System.out.println(student));
});
session.commit();
session.close();
- 结果
==> Preparing: select * from WEB_CLASS
==> Parameters:
<== Total: 2
==> Preparing: select * from STUDENT where class_id = ?
==> Parameters: 2(Integer)
<== Total: 2
WebClass [id=2, code=C002, name=无限流战斗班]
Student [id=2, name=王怡, sex=女, age=24]
Student [id=4, name=王多燕, sex=女, age=26]
==> Preparing: select * from STUDENT where class_id = ?
==> Parameters: 1(Integer)
<== Total: 2
WebClass [id=1, code=C001, name=大乱斗指导班]
Student [id=1, name=王一倩, sex=女, age=22]
Student [id=3, name=王二赞, sex=男, age=28]
7.2 一对多映射
7.2.1 mybatis配置
- mybatis-config.xml添加如下配置
7.2.2 java bean
- 同 6.1.1
7.2.3 mapper映射文件
- WebClassMapper.xml
ID, CODE, NAME
7.2.4 mapper接口
- WebClassMapper.xml
public interface WebClassMapper {
WebClass selectWebClassById(int i);
}
7.2.5 测试类
public class OneToManyTest {
public static void main(String[] args) {
SqlSession session = SqlSessionFactoryUtil.getSession();
OneToManyTest test = new OneToManyTest();
//测试一对多
test.testOneToMany(session);
//测试多对一
//test.testManyToOne(session);
session.commit();
session.close();
}
//测试一对多，查询班级（一）级联查询学生（多）
public void testOneToMany(SqlSession session) {
WebClassMapper mapper = session.getMapper(WebClassMapper.class);
WebClass webClass = mapper.selectWebClassById(1);
System.out.println(webClass.getId()+" "+webClass.getCode()+" "+webClass.getName());
System.out.println(webClass.toString());
List students = webClass.getStudents();
for (Student student : students) {
System.out.println(student.toString());
}
}
}
==> Preparing: select ID, CODE, NAME from WEB_CLASS where ID = ?
==> Parameters: 1(Integer)
<== Total: 1
1 C001 大乱斗指导班
==> Preparing: select ID as studentId, NAME as studentName, SEX, AGE, CLASS_ID from STUDENT where CLASS_ID = ?
==> Parameters: 1(Integer)
<== Total: 4
WebClass [id=1, code=C001, name=大乱斗指导班]
Student [id=1, name=王一倩, sex=女, age=22]
Student [id=2, name=王怡, sex=女, age=24]
Student [id=3, name=王二赞, sex=男, age=28]
Student [id=4, name=王多燕, sex=女, age=26]
7.3 多对一映射
7.3.1 java bean
- 同 6.1.1
7.3.2 mapper配置
- StudentMapper.xml
ID as studentId, NAME as studentName, SEX, AGE, CLASS_ID
${student}.ID as studentId, ${student}.NAME as studentName, ${student}.SEX, ${student}.AGE, ${student}.CLASS_ID
${webClass}.ID , ${webClass}.CODE, ${webClass}.NAME
7.3.3 mapper接口
- StudentMapper.java
public interface StudentMapper {
Student selectStudentById(int id);
List selectStudentByClassId(int classId);
}
7.3.4 测试类
public class OneToManyTest {
//测试多对一，查询学生（多）级联查询班级（一）
public void testManyToOne(SqlSession session) {
StudentMapper studentMapper = session.getMapper(StudentMapper.class);
Student student = studentMapper.selectStudentById(1);
System.out.println(student);
System.out.println(student.getWebClass().toString());
}
- 结果
==> Preparing: select s.ID as studentId, s.NAME as studentName, s.SEX, s.AGE, s.CLASS_ID , c.ID , c.CODE, c.NAME from STUDENT s,WEB_CLASS c where s.class_id=c.id and s.ID = ?
==> Parameters: 1(Integer)
<== Total: 1
Student [id=1, name=王一倩, sex=女, age=22]
WebClass [id=1, code=C001, name=大乱斗指导班]
7.4 多对多映射
7.4.1 java bean
public class WebOrder {
private BigDecimal id;
private String code;
private BigDecimal total;
private BigDecimal userId;
//订单和用户是多对一关系
private WebUser user;
//订单和商品是多对多关系
private List articles;
}
public class WebUser {
private BigDecimal id;
private String username;
private String loginname;
private String password;
private String phone;
private String address;
//用户和订单是一对多关系
private List orders;
}
public class WebArticle {
private BigDecimal id;
private String name;
private BigDecimal price;
private String remark;
}
7.4.2 mapper配置
- WebOrderMapper.xml
ID, USERNAME, LOGINNAME, PASSWORD, PHONE, ADDRESS
ID, NAME, PRICE, REMARK
7.4.3 mapper接口
public interface WebOrderMapper {
List selectOrderByUserId(int userId);
WebOrder selectOrderById(int id);
}
public interface WebUserMapper {
WebUser selectUserById(int id);
}
7.4.4 测试类
public class ManyToManyTest {
public static void main(String[] args) {
SqlSession session = SqlSessionFactoryUtil.getSession();
ManyToManyTest test = new ManyToManyTest();
//test.testOneToMany(session);
test.testManyToMany(session);
session.commit();
session.close();
}
public void testOneToMany(SqlSession session) {
WebUserMapper userMapper = session.getMapper(WebUserMapper.class);
WebUser user = userMapper.selectUserById(1);
System.out.println(user.getUsername()+" "+user.getLoginname()+" "+user.getPhone()+" "+user.getAddress());
List orders = user.getOrders();
for (WebOrder webOrder : orders) {
System.out.println(webOrder.toString());
}
}
public void testManyToMany(SqlSession session) {
WebOrderMapper orderMapper = session.getMapper(WebOrderMapper.class);
WebOrder order = orderMapper.selectOrderById(1);
System.out.println(order.getCode()+" "+order.getTotal());
WebUser user = order.getUser();
System.out.println(user.toString());
List articles = order.getArticles();
for (WebArticle webArticle : articles) {
System.out.println(webArticle.toString());
}
}
}