mybatis xml多表查询，子查询，连接查询，动态sql
项目结构
数据库表
student_type 表
student 表
依赖
mysql
mysql-connector-java
8.0.30
org.mybatis
mybatis
3.5.5
junit
junit
4.12
test
实体类
Student 类
一个学生只有一个年级
package com.tmg.domain;
public class Student {
private int id;
private String name;
private int age;
private String email;
private Integer typeId;
private Type type;
public Integer getTypeId() {
return typeId;
}
public void setTypeId(Integer typeId) {
this.typeId = typeId;
}
public Type getType() {
return type;
}
public void setType(Type type) {
this.type = type;
}
public Student(int id, String name, int age, String email) {
this.id = id;
this.name = name;
this.age = age;
this.email = email;
}
public Student() {
}
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 getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
@Override
public String toString() {
return "Student{" +
"id=" + id +
", name='" + name + '\'' +
", age=" + age +
", email='" + email + '\'' +
", typeId=" + typeId +
// ", type=" + type +
'}';
}
}
Type 类
一个年级有多个学生，所以用 list
package com.tmg.domain;
import java.util.List;
public class Type {
private Integer id;
private String name;
private List students;
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 List getStudents() {
return students;
}
public void setStudents(List students) {
this.students = students;
}
@Override
public String toString() {
return "Type{" +
"id=" + id +
", name='" + name + '\'' +
// ", students=" + students +
'}';
}
}
StudentDao
package com.tmg.dao;
import com.tmg.domain.Student;
import org.apache.ibatis.annotations.Param;
import java.util.List;
public interface StudentDao {
//多个参数的配置
void insertEmp( @Param("stuName") String name,
@Param("stuAge") int age, @Param("stuEmail") String email);
List selectByStudent(Student student);
void update(Student employee);
void update2(Student employee);
List selectByIds(@Param("ids") int []id);
// List selectById(int id);
List selectByTypeId(int id);
List selectAll();
}
TypeDao
package com.tmg.dao;
import com.tmg.domain.Type;
import java.util.List;
public interface TypeDao {
List selectAll();
Type selectById(Integer id);
}
mybatis-config.xml配置数据源，日志等
TypeDao.xml
下列代码中：
1 resultMap 里面property对应实体类属性，column对应数据库字段名
2 主键用 id 标签 其他用result
3 关联查询(子查询和连接查询) 连接查询查一次
4 一个年级多个学生，所以用collection 如果一对一用association
StudentDao.xml
动态sql不理解可看以下博客：
https://blog.csdn.net/weixin_57689217/article/details/135707991?csdn_share_tail=%7B%22type%22%3A%22blog%22%2C%22rType%22%3A%22article%22%2C%22rId%22%3A%22135707991%22%2C%22source%22%3A%22weixin_57689217%22%7D
insert into student( id,name,age,email) values (#{id},#{name},#{age},#{email});
select * from student
update student
stu_age=#{age},
stu_email=#{email},
stu_name=#{name},
where stu_id=#{id};
update student
stu_age=#{age},
stu_email=#{email},
stu_name=#{name},
where stu_id=#{id};
TypeDaoText 测试类
package com.tmg.dao;
import com.tmg.domain.Type;
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 java.io.IOException;
import java.util.List;
public class TypeDaoText {
@Test
public void testselectAll() throws IOException {
SqlSessionFactory build = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = build.openSession();
TypeDao mapper = sqlSession.getMapper(TypeDao.class);
List typeList = mapper.selectAll();
for (Type type : typeList) {
System.out.println(type);
}
}
@Test
public void testselectById() throws IOException {
SqlSessionFactory build = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = build.openSession();
TypeDao mapper = sqlSession.getMapper(TypeDao.class);
Type type = mapper.selectById(1);
System.out.println(type);
}
}
StudentDaoText 测试类
package com.tmg.dao;
import com.tmg.domain.Student;
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 java.io.IOException;
import java.util.List;
public class StudentDaoText {
@Test
public void testinsertEmp() throws IOException {
SqlSessionFactoryBuilder factoryBuilder = new SqlSessionFactoryBuilder();
SqlSessionFactory factory = factoryBuilder.build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = factory.openSession();
StudentDao mapper = sqlSession.getMapper(StudentDao.class);
mapper.insertEmp("tmg",18,"[email protected]");
sqlSession.commit();
}
@Test
public void testselectByStudent() throws IOException {
SqlSessionFactory build = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = build.openSession();
StudentDao mapper = sqlSession.getMapper(StudentDao.class);
Student student = new Student();
// student.setName("z");
// student.setAge(18);
// student.setEmail("[email protected]");
List students = mapper.selectByStudent(student);
for (Student student1 : students){
System.out.println(student1);
}
}
@Test
public void testupdate() throws IOException {
//创建会话工厂构建器
SqlSessionFactoryBuilder factoryBuilder = new SqlSessionFactoryBuilder();
SqlSessionFactory build = factoryBuilder.build(Resources.getResourceAsStream("mybatis-config.xml"));
//创建会话
SqlSession sqlSession = build.openSession();
//获得Mapper对象
StudentDao mapper = sqlSession.getMapper(StudentDao.class);
Student student = new Student();
// student.setName();
student.setId(1);
student.setAge(22);
mapper.update(student);
sqlSession.commit();
}
@Test
public void testupdate2() throws IOException {
SqlSessionFactoryBuilder factoryBuilder = new SqlSessionFactoryBuilder();
SqlSessionFactory build = factoryBuilder.build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = build.openSession();
StudentDao mapper = sqlSession.getMapper(StudentDao.class);
Student student = new Student();
student.setId(1);
student.setAge(44);
mapper.update2(student);
sqlSession.commit();
}
@Test
public void testselectByIds() throws IOException {
SqlSessionFactory build = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = build.openSession();
StudentDao mapper = sqlSession.getMapper(StudentDao.class);
int []a={1};
List students = mapper.selectByIds(a);
for (Student student:students){
System.out.println(student);
System.out.println(student.getType());
}
}
@Test
public void testselectAll() throws IOException {
SqlSessionFactory build = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = build.openSession();
StudentDao mapper = sqlSession.getMapper(StudentDao.class);
List students = mapper.selectAll();
for(Student student : students){
System.out.println(student);
System.out.println(student.getType());
}
}
}