小峰mybatis（4）mybatis使用注解配置sql映射器

2023-08-04 21:05:34

主流开发还是使用xml来配置；使用注解配置比较快，但是不支持所有功能；有些功能还是得用配置文件；

一、基本映射语句：　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

@Inert

@Update

@Delete

@Select

二、结果集映射语句　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

项目结够：

Student.java model实体类：

package com.cy.model;

public class Student{

    private Integer id;

    private String name;

    private Integer age;

    public Student(){

    }

    public Student(String name, Integer age){

        this.name = name;

        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 Integer getAge() {

        return age;

    }

    public void setAge(Integer age) {

        this.age = age;

    }

    @Override

    public String toString() {

        return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";

    }

}

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="jdbc.properties"/>

    <!-- 别名 -->

    <typeAliases>

        <package name="com.cy.model"/>

    </typeAliases>

    <environments default="development">

        <environment id="development">

            <transactionManager type="JDBC" />

                <dataSource type="POOLED">

                    <property name="driver" value="${jdbc.driverClassName}" />

                    <property name="url" value="${jdbc.url}" />

                    <property name="username" value="${jdbc.username}" />

                    <property name="password" value="${jdbc.password}" />

                </dataSource>

        </environment>

        <environment id="test">

            <transactionManager type="JDBC" />

            <dataSource type="POOLED">

                <property name="driver" value="${jdbc.driverClassName}" />

                <property name="url" value="${jdbc.url}" />

                <property name="username" value="${jdbc.username}" />

                <property name="password" value="${jdbc.password}" />

            </dataSource>

        </environment>

    </environments>

    <mappers>

        <package name="com.cy.mapper"/>

    </mappers>

</configuration>

StudentMapper.java 接口：

package com.cy.mapper;

import java.util.List;

import org.apache.ibatis.annotations.Delete;

import org.apache.ibatis.annotations.Insert;

import org.apache.ibatis.annotations.Result;

import org.apache.ibatis.annotations.Results;

import org.apache.ibatis.annotations.Update;

import org.apache.ibatis.annotations.Select;

import com.cy.model.Student;

public interface StudentMapper {

    //插入

    @Insert("insert into t_student values(null, #{name}, #{age})")

    public int inertStudent(Student student);

    //更新

    @Update("update t_student set name=#{name}, age=#{age} where id = #{id}")

    public int updateStudent(Student stu);

    //删除

    @Delete("delete from t_student where id=#{id}")

    public int deleteStudent(int id);

    //根据id查找学生

    @Select("select * from t_student where id=#{id}")

    public Student getStudentById(Integer id);

    //查询所有学生  结果集映射  id主键列

    @Select("select * from t_student")

    @Results(

            {

                @Result(id=true,column="id",property="id"),

                @Result(column="name",property="name"),

                @Result(column="age",property="age")

            }

    )

    public List<Student> findStudents();

}

测试代码StudentTest.java:

package com.cy.service;

import java.util.List;

import org.apache.ibatis.session.SqlSession;

import org.apache.log4j.Logger;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;

import com.cy.mapper.StudentMapper;

import com.cy.model.Student;

import com.cy.util.SqlSessionFactoryUtil;

public class StudentTest {

    private static Logger logger = Logger.getLogger(StudentTest.class);

    private SqlSession sqlSession=null;

    private StudentMapper studentMapper=null;

    @Before

    public void setUp() throws Exception {

        sqlSession=SqlSessionFactoryUtil.openSession();

        studentMapper=sqlSession.getMapper(StudentMapper.class);

    }

    @After

    public void tearDown() throws Exception {

        sqlSession.close();

    }

    @Test

    public void testInsertStudent() {

        logger.info("测试insertStudent");

        Student stu = new Student("cpp", 12);

        int count = studentMapper.inertStudent(stu);

        sqlSession.commit();

    }

    @Test

    public void testUpdateStudent() {

        logger.info("测试updateStudent");

        Student stu = new Student("cppp", 13);

        stu.setId(14);

        int count = studentMapper.updateStudent(stu);

        sqlSession.commit();

    }

    @Test

    public void testDeleteStudent() {

        logger.info("测试删除学生");

        int count = studentMapper.deleteStudent(14);

        sqlSession.commit();

    }

    @Test

    public void testGetById(){

        logger.info("根据id查找学生");

        Student stu = studentMapper.getStudentById(1);

        System.out.println(stu);

    }

    @Test

    public void testFindStudent() {

        logger.info("测试查询所有学生");

        List<Student> students = studentMapper.findStudents();

        for(Student student : students){

            System.out.println(student);

        }

    }

}

三、使用注解一对一映射：　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

每个学生都有一个地址，一对一；

数据库中t_student和t_address：

t_address:

Student.java 实体：

package com.cy.model;

public class Student{

    private Integer id;

    private String name;

    private Integer age;

    private Address address;

    public Student(){

    }

    public Student(String name, Integer age){

        this.name = name;

        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 Integer getAge() {

        return age;

    }

    public void setAge(Integer age) {

        this.age = age;

    }

    public Address getAddress() {

        return address;

    }

    public void setAddress(Address address) {

        this.address = address;

    }

    @Override

    public String toString() {

        return "Student [id=" + id + ", name=" + name + ", age=" + age

                + ", address=" + address + "]";

    }

}

Address.java 实体：

package com.cy.model;

public class Address {

    private Integer id;

    private String sheng;

    private String shi;

    private String qu;

    public Integer getId() {

        return id;

    }

    public void setId(Integer id) {

        this.id = id;

    }

    public String getSheng() {

        return sheng;

    }

    public void setSheng(String sheng) {

        this.sheng = sheng;

    }

    public String getShi() {

        return shi;

    }

    public void setShi(String shi) {

        this.shi = shi;

    }

    public String getQu() {

        return qu;

    }

    public void setQu(String qu) {

        this.qu = qu;

    }

    @Override

    public String toString() {

        return "Address [id=" + id + ", sheng=" + sheng + ", shi=" + shi

                + ", qu=" + qu + "]";

    }

}

StudentMapper.java接口：

//查询学生，带地址

    @Select("select * from t_student where id=#{id}")

    @Results(

            {

                @Result(id=true,column="id",property="id"),

                @Result(column="name",property="name"),

                @Result(column="age",property="age"),

                @Result(column="addressId",property="address",one=@One(select="com.cy.mapper.AddressMapper.findById"))

            }

    )

    public Student findStudentWithAddress(int id);

AddressMapper.java接口：

public interface AddressMapper {

    @Select("select * from t_address where id=#{id}")

    public Address findById(Integer id);

}

mybatis的实现是：在查找学生的时候，将addressId,传到AddressMapper.findById方法，根据这个addressId查找address；

测试代码：

@Test

    public void testFindStudentWithAddress() {

        logger.info("测试学生,带地址");

        Student student = studentMapper.findStudentWithAddress(15);

        System.out.println(student);

    }

console打印：

四、使用注解，一对多映射　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

一个年级下有多个学生，多个学生属于一个年级，年级和学生是一对多；

Student.java:

package com.cy.model;

public class Student{

    private Integer id;

    private String name;

    private Integer age;

    private Address address;

    private Grade grade;

    public Student(){

    }

    public Student(String name, Integer age){

        this.name = name;

        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 Integer getAge() {

        return age;

    }

    public void setAge(Integer age) {

        this.age = age;

    }

    public Address getAddress() {

        return address;

    }

    public void setAddress(Address address) {

        this.address = address;

    }

    public Grade getGrade() {

        return grade;

    }

    public void setGrade(Grade grade) {

        this.grade = grade;

    }

    @Override

    public String toString() {

        return "Student [id=" + id + ", name=" + name + ", age=" + age

                + ", address=" + address + ", grade=" + grade + "]";

    }

}

Grade.java:

package com.cy.model;

import java.util.List;

public class Grade {

    private Integer id;

    private String gradeName;

    private List<Student> students;

    public Integer getId() {

        return id;

    }

    public void setId(Integer id) {

        this.id = id;

    }

    public String getGradeName() {

        return gradeName;

    }

    public void setGradeName(String gradeName) {

        this.gradeName = gradeName;

    }

    public List<Student> getStudents() {

        return students;

    }

    public void setStudents(List<Student> students) {

        this.students = students;

    }

    @Override

    public String toString() {

        return "Grade [id=" + id + ", gradeName=" + gradeName +"]";

    }

}

数据库中表，t_student:

小峰mybatis（4）mybatis使用注解配置sql映射器

t_grade:

小峰mybatis（4）mybatis使用注解配置sql映射器

1)根据id查找年级，将年级下的学生也查出来：

GradeMapper.java:

public interface GradeMapper {

    //根据id查找年级，将年级下的学生也查出来

    @Select("select * from t_grade where id = #{id}")

    @Results(

            {

                @Result(id=true,column="id",property="id"),

                @Result(column="gradeName",property="gradeName"),

                @Result(column="id",property="students",many=@Many(select="com.cy.mapper.StudentMapper.findStudentByGradeId"))

            }

    )

    public Grade findById(Integer id);

}

StudentMapper.java:

//根据年级查找学生

    @Select("select * from t_student where gradeId=#{gradeId}")

    @Results(

            {

                @Result(id=true,column="id",property="id"),

                @Result(column="name",property="name"),

                @Result(column="age",property="age"),

                @Result(column="addressId",property="address",one=@One(select="com.cy.mapper.AddressMapper.findById"))

            }

    )

    public Student findStudentByGradeId(int gradeId);

测试代码：

//根据id查找年级，将年级下的学生也查出来

    @Test

    public void testFindGradeWithStudents() {

        logger.info("根据id查询年级(带学生)");

        Grade grade=gradeMapper.findById(1);

        System.out.println(grade);

        List<Student> studentList=grade.getStudents();

        for(Student student:studentList){

            System.out.println(student);

        }

    }

结果：

小峰mybatis（4）mybatis使用注解配置sql映射器

2）根据id查询学生，将年级信息也查出来：

StudentMapper.java:

//根据id查询学生带地址   和 年级

    @Select("select * from t_student where id=#{id}")

    @Results(

            {

                @Result(id=true,column="id",property="id"),

                @Result(column="name",property="name"),

                @Result(column="age",property="age"),

                @Result(column="addressId",property="address",one=@One(select="com.cy.mapper.AddressMapper.findById")),

                @Result(column="gradeId",property="grade",one=@One(select="com.cy.mapper.GradeMapper.findById"))

            }

    )

    public Student findStudentWithAddressAndGrade(int id);

GradeMapper.java中的findById和上面1）中一样；

测试代码：

//根据id查询学生，带地址和年级

    @Test

    public void testSelectStudentWithAddressAndGrade() {

        logger.info("根据id查询学生(带地址、年级)");

        Student student=studentMapper.findStudentWithAddressAndGrade(1);

        System.out.println(student);

    }

打印结果：

小峰mybatis（4）mybatis使用注解配置sql映射器

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