springboot整合mybatis-plus基于注解实现一对一(一对多)查询功能

<?xml version= "1.0" encoding= "UTF-8" ?>

<project xmlns= "http://maven.apache.org/POM/4.0.0" xmlns:xsi= "http://www.w3.org/2001/XMLSchema-instance"

          xsi:schemaLocation= "http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" >

     <modelVersion> 4.0 . 0 </modelVersion>

     <parent>

         <groupId>org.springframework.boot</groupId>

         <artifactId>spring-boot-starter-parent</artifactId>

         <version> 2.1 . 4 .RELEASE</version>

         <relativePath/> <!-- lookup parent from repository -->

     </parent>

     <groupId>com.lyb</groupId>

     <artifactId>spring-mybatis-demo</artifactId>

     <version> 0.0 . 1 -SNAPSHOT</version>

     <packaging>jar</packaging>

     <name>spring-mybatis-demo</name>

     <description>Demo project for Spring Boot</description>

     <properties>

         <project.build.sourceEncoding>UTF- 8 </project.build.sourceEncoding>

         <project.reporting.outputEncoding>UTF- 8 </project.reporting.outputEncoding>

         <java.version> 1.8 </java.version>

     </properties>

     <dependencies>

         <!--

         <dependency>

             <groupId>org.mybatis.spring.boot</groupId>

             <artifactId>mybatis-spring-boot-starter</artifactId>

             <version> 2.0 . 0 </version>

         </dependency>

         -->

         <dependency>

             <groupId>com.baomidou</groupId>

             <artifactId>mybatis-plus-boot-starter</artifactId>

             <version> 3.1 . 1 </version>

         </dependency>

         <dependency>

             <groupId>org.projectlombok</groupId>

             <artifactId>lombok</artifactId>

             <version> 1.18 . 8 </version>

             <scope>provided</scope>

         </dependency>

         <dependency>

             <groupId>com.baomidou</groupId>

             <artifactId>mybatis-plus</artifactId>

             <version> 3.1 . 1 </version>

         </dependency>

         <dependency>

             <groupId>mysql</groupId>

             <artifactId>mysql-connector-java</artifactId>

             <scope>runtime</scope>

         </dependency>

         <dependency>

             <groupId>com.baomidou</groupId>

             <artifactId>mybatis-plus-generator</artifactId>

             <version> 3.1 . 1 </version>

         </dependency>

         <dependency>

             <groupId>org.springframework.boot</groupId>

             <artifactId>spring-boot-starter-test</artifactId>

             <scope>test</scope>

         </dependency>

     </dependencies>

     <build>

         <plugins>

             <plugin>

                 <groupId>org.springframework.boot</groupId>

                 <artifactId>spring-boot-maven-plugin</artifactId>

             </plugin>

         </plugins>

     </build>

</project>

spring:

   datasource:

     url: jdbc:mysql: //127.0.0.1:3306/demo?useUnicode=true&characterEncoding=utf8&serverTimezone=UTC

     username: root

     password: liuyabin

     driver- class -name: com.mysql.jdbc.Driver

mybatis-plus:

   type-aliases- package : com.lyb.springmybatisdemo.entity

   type-aliases- super -type: java.lang.Object

package com.lyb.springmybatisdemo.entity;

import com.baomidou.mybatisplus.annotation.IdType;

import com.baomidou.mybatisplus.annotation.TableField;

import com.baomidou.mybatisplus.annotation.TableId;

import com.baomidou.mybatisplus.annotation.TableName;

import lombok.*;

@Data

@Builder

@ToString

@EqualsAndHashCode

@NoArgsConstructor

@AllArgsConstructor

@TableName (value = "student" )

public class Student {

     @TableId (value = "Id" ,type = IdType.AUTO)

     private int id;

     @TableField (value = "SName" ,exist = true ,select = true )

     private String name;

     @TableField (value = "Age" )

     private int age;

     @TableField (value = "ClassId" )

     private int classId;

     @TableField (exist = false )

     private StudentClass studentClass;

}

package com.lyb.springmybatisdemo.entity;

import com.baomidou.mybatisplus.annotation.IdType;

import com.baomidou.mybatisplus.annotation.TableField;

import com.baomidou.mybatisplus.annotation.TableId;

import com.baomidou.mybatisplus.annotation.TableName;

import lombok.*;

@Data

@Builder

@ToString

@EqualsAndHashCode

@NoArgsConstructor

@AllArgsConstructor

@TableName (value = "stuClass" )

public class StudentClass {

     @TableId (value = "ClassId" ,type = IdType.AUTO)

     private int classId;

     @TableField (value = "ClassName" )

     private String className;

}

package com.lyb.springmybatisdemo.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;

import com.lyb.springmybatisdemo.entity.StudentClass;

import org.apache.ibatis.annotations.Mapper;

@Mapper

public interface StudentClassMapper extends BaseMapper<StudentClass> {

}

package com.lyb.springmybatisdemo.mapper;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;

import com.lyb.springmybatisdemo.entity.Student;

import org.apache.ibatis.annotations.*;

import java.util.List;

@Mapper

public interface StudentMapper extends BaseMapper<Student> {

     @Results (id= "stuMap" ,value = {

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

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

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

             @Result (property = "classId" ,column = "ClassID" ),

             @Result (property = "studentClass" ,column = "ClassID" ,one = @One (select = "com.lyb.springmybatisdemo.mapper.StudentClassMapper.selectById" ))

     })

     @Select ( "SELECT * FROM STUDENT WHERE ID=#{id}" )

     Student findStudentById( int id);

     @Select ( "select * from Student where 1=1 and " +

             "${ew.sqlSegment}" )

     @ResultMap (value = "stuMap" )

     List<Student> selectStudents( @Param ( "ew" ) QueryWrapper<Student> wrapper);

}

package com.lyb.springmybatisdemo;

import com.baomidou.mybatisplus.core.conditions.Wrapper;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;

import com.lyb.springmybatisdemo.entity.Student;

import com.lyb.springmybatisdemo.mapper.StudentMapper;

import org.junit.Assert;

import org.junit.Test;

import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.boot.test.context.SpringBootTest;

import org.springframework.test.context.junit4.SpringRunner;

import java.util.List;

@RunWith (SpringRunner. class )

@SpringBootTest

public class SpringMybatisDemoApplicationTests {

     @Autowired

     private StudentMapper studentMapper;

     @Test

     public   void testByWrapper(){

         QueryWrapper<Student> queryWrapper = new QueryWrapper<Student>();

         queryWrapper.lambda().eq(Student::getAge, 2 )

                             .eq(Student::getClassId, 1 );

         List<Student> students = studentMapper.selectStudents(queryWrapper);

     }

}

package com.lyb.springmybatisdemo;

import org.mybatis.spring.annotation.MapperScan;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication

@MapperScan ( "com.lyb.springmybatisdemo.mapper" )

public class SpringMybatisDemoApplication {

     public static void main(String[] args) {

         SpringApplication.run(SpringMybatisDemoApplication. class , args);

     }

}