JpaRepository的关联查询和@Query查询

爱被打了一巴掌 2021-07-24 19:25 354阅读 0赞

**一 pom**

<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>
         <groupId>org.fkit</groupId>
         <artifactId>springdatajpaquerytest</artifactId>
         <version>0.0.1-SNAPSHOT</version>
         <packaging>jar</packaging>
         <name>springdatajpaquerytest</name>
         <url>http://maven.apache.org</url>
         
         <parent>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-starter-parent</artifactId>
               <version>2.0.0.RELEASE</version>
               <relativePath />
         </parent>
         <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.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-web</artifactId>
               </dependency>
               
               <dependency>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-thymeleaf</artifactId>
               </dependency>
               
               <dependency>
                    <groupId>mysql</groupId>
                    <artifactId>mysql-connector-java</artifactId>
               </dependency>
               
               <dependency>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-data-jpa</artifactId>
               </dependency>
               <dependency>
                    <groupId>junit</groupId>
                    <artifactId>junit</artifactId>
                    <scope>test</scope>
               </dependency>
         </dependencies>
    </project>

**二 启动类**

package org.fkit.springdatajpaquerytest;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    
    @SpringBootApplication
    public class App
    {
        public static void main( String[] args )
        {
            // SpringApplication 用于从main方法启动Spring应用的类。
            SpringApplication.run(App.class, args);
        }
    }

**三 配置文件**

########################################################
    ### \u6570\u636E\u6E90\u4FE1\u606F\u914D\u7F6E
    ########################################################
    # \u6570\u636E\u5E93\u5730\u5740
    spring.datasource.url=jdbc:mysql://localhost:3306/springdatajpaquery
    # \u7528\u6237\u540D
    spring.datasource.username=root
    # \u5BC6\u7801
    spring.datasource.password=
    # \u6570\u636E\u5E93\u9A71\u52A8
    spring.datasource.driverClassName=com.mysql.jdbc.Driver
    #  \u6307\u5B9A\u8FDE\u63A5\u6C60\u4E2D\u6700\u5927\u7684\u6D3B\u8DC3\u8FDE\u63A5\u6570.
    spring.datasource.max-active=20
    #  \u6307\u5B9A\u8FDE\u63A5\u6C60\u6700\u5927\u7684\u7A7A\u95F2\u8FDE\u63A5\u6570\u91CF.
    spring.datasource.max-idle=8
    #  \u6307\u5B9A\u5FC5\u987B\u4FDD\u6301\u8FDE\u63A5\u7684\u6700\u5C0F\u503C
    spring.datasource.min-idle=8
    #  \u6307\u5B9A\u542F\u52A8\u8FDE\u63A5\u6C60\u65F6\uFF0C\u521D\u59CB\u5EFA\u7ACB\u7684\u8FDE\u63A5\u6570\u91CF
    spring.datasource.initial-size=10
    ########################################################
    ### JPA\u6301\u4E45\u5316\u914D\u7F6E
    ########################################################
    # \u6307\u5B9A\u6570\u636E\u5E93\u7684\u7C7B\u578B
    spring.jpa.database=MySQL
    #  \u6307\u5B9A\u662F\u5426\u9700\u8981\u5728\u65E5\u5FD7\u4E2D\u663E\u793Asql\u8BED\u53E5
    spring.jpa.show-sql=true
    #  \u6307\u5B9A\u81EA\u52A8\u521B\u5EFA|\u66F4\u65B0|\u9A8C\u8BC1\u6570\u636E\u5E93\u8868\u7ED3\u6784\u7B49\u914D\u7F6E\uFF0C\u914D\u7F6E\u6210update
    #  \u8868\u793A\u5982\u679C\u6570\u636E\u5E93\u4E2D\u5B58\u5728\u6301\u4E45\u5316\u7C7B\u5BF9\u5E94\u7684\u8868\u5C31\u4E0D\u521B\u5EFA\uFF0C\u4E0D\u5B58\u5728\u5C31\u521B\u5EFA\u5BF9\u5E94\u7684\u8868
    spring.jpa.hibernate.ddl-auto=update
    # Naming strategy
    # \u6307\u5B9A\u547D\u540D\u7B56\u7565
    spring.jpa.hibernate.naming-strategy=org.hibernate.cfg.ImprovedNamingStrategy
    # \u6307\u5B9A\u6570\u636E\u5E93\u65B9\u8A00
    spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5Dialect

**四 新建数据库springdatajpaquery**

**五 实体类**

1 Clazz

package org.fkit.springdatajpaquerytest.bean;
    
    
    import java.io.Serializable;
    import java.util.HashSet;
    import java.util.Set;
    import javax.persistence.Entity;
    import javax.persistence.FetchType;
    import javax.persistence.GeneratedValue;
    import javax.persistence.GenerationType;
    import javax.persistence.Id;
    import javax.persistence.OneToMany;
    import javax.persistence.Table;
    
    
    @Entity
    @Table(name="tb_clazz")
    public class Clazz implements Serializable{
        
        private static final long serialVersionUID = 1L;
        
        @Id
        @GeneratedValue(strategy=GenerationType.IDENTITY)
        private int code ;
        private String name ;
        // 班级与学生是一对多的关联
        @OneToMany(
                   fetch=FetchType.LAZY,
                   targetEntity=Student.class,
                   mappedBy="clazz"
                )     
        private Set<Student> students = new HashSet<>();
        
        public Clazz() {
            
        }
        // 班级对象
        public Clazz(String name) {
            this.name = name;
        }
        public int getCode() {
            return code;
        }
        public void setCode(int code) {
            this.code = code;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public Set<Student> getStudents() {
            return students;
        }
        public void setStudents(Set<Student> students) {
            this.students = students;
        }
    }

2 Student

package org.fkit.springdatajpaquerytest.bean;
    
    
    import java.io.Serializable;
    
    
    import javax.persistence.Entity;
    import javax.persistence.FetchType;
    import javax.persistence.GeneratedValue;
    import javax.persistence.GenerationType;
    import javax.persistence.Id;
    import javax.persistence.JoinColumn;
    import javax.persistence.ManyToOne;
    import javax.persistence.Table;
    
    
    @Entity
    @Table(name="tb_student")
    public class Student implements Serializable{
        
        private static final long serialVersionUID = 1L;
        
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private int id;
        private String name ;
        private String address ;
        private int age ;
        private char sex;
        // 学生与班级是多对一的关系，这里配置的是双向关联
        @ManyToOne(fetch=FetchType.LAZY,
                targetEntity=Clazz.class
                )
        @JoinColumn(name="clazzId",referencedColumnName="code")
        private Clazz clazz ;
        public Student() {
    
    
        }
        public Student(String name, String address, int age, char sex,
                Clazz clazz) {
            super();
            this.name = name;
            this.address = address;
            this.age = age;
            this.sex = sex;
            this.clazz = clazz;
        }
        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 String getAddress() {
            return address;
        }
        public void setAddress(String address) {
            this.address = address;
        }
        public int getAge() {
            return age;
        }
        public void setAge(int age) {
            this.age = age;
        }
        public char getSex() {
            return sex;
        }
        public void setSex(char sex) {
            this.sex = sex;
        }
        public Clazz getClazz() {
            return clazz;
        }
        public void setClazz(Clazz clazz) {
            this.clazz = clazz;
        }
    }

**六 控制器**

package org.fkit.springdatajpaquerytest.controller;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Map;
    import javax.annotation.Resource;
    import org.fkit.springdatajpaquerytest.bean.Clazz;
    import org.fkit.springdatajpaquerytest.bean.Student;
    import org.fkit.springdatajpaquerytest.service.SchoolService;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    
    @RestController
    @RequestMapping("/student")
    public class StudentController {
        
        // 注入ShcoolService
        @Resource
        private SchoolService schoolService;
        @RequestMapping("/save")
        public String save() {
            
            Clazz clazz1 = new Clazz("疯狂java开发1班");
            Clazz clazz2 = new Clazz("疯狂java开发2班");
            // 保存班级对象数据
            List<Clazz> clazzs = new ArrayList<>();
            clazzs.add(clazz1);
            clazzs.add(clazz2);
            schoolService.saveClazzAll(clazzs);
            
            Student swk = new Student("孙悟空","广州",700,'男',clazz1);
            Student zzj = new Student("蜘蛛精","广州",700,'女',clazz1);
            Student nmw = new Student("牛魔王","广州",500,'男',clazz2);
            
            List<Student> students = new ArrayList<>();
            students.add(swk);
            students.add(zzj);
            students.add(nmw);
            schoolService.saveStudentAll(students);
            return "保存学生对象成功";
        }
        /**
         * 查询某个班级下所有的学生姓名，年龄，性别
         * @param clazzName
         * @return
         */
        @RequestMapping("/getClazzStus")
        public List<Map<String, Object>> getClazzStus(String clazzName){
            return schoolService.getStusByClazzName(clazzName);
        }
        /**
         * 查询某个班级下所有的学生姓名，性别
         * @param clazzName
         * @return
         */
        @RequestMapping("/findNameAndSexByClazzName")
        public List<Map<String, Object>> findNameAndSexByClazzName(String clazzName){
            return schoolService.findNameAndSexByClazzName(clazzName);
        }
        /**
         * ，查询某个班级下某种性别的所有学生的姓名
         * @param clazzName
         * @return
         */
        @RequestMapping("/findNameByClazzNameAndSex")
        public List<String> findNameByClazzNameAndSex(String clazzName ,Character sex){
            return schoolService.findNameByClazzNameAndSex(clazzName ,sex);
        }
        /**
         * 查询某个学生属于哪个班级
         * @param clazzName
         * @return
         */
        @RequestMapping("/findClazzNameByStuName")
        public String findClazzNameByStuName(String stuName){
            return schoolService.findClazzNameByStuName(stuName);
        }
        /**
         * 删除某个学生对象
         * @param clazzName
         * @return
         */
        @RequestMapping("/deleteStuByStuName")
        public String deleteStuByStuName(String stuName){
            return "删除数据："+schoolService.deleteStuByStuName(stuName);
        }
        
    }

**七 Repository层**

1 ClazzRepository

package org.fkit.springdatajpaquerytest.repository;
    import org.fkit.springdatajpaquerytest.bean.Clazz;
    import org.springframework.data.jpa.repository.JpaRepository;
    
    public interface ClazzRepository extends JpaRepository<Clazz, Integer> {
        
    }

2 StudentRepository

package org.fkit.springdatajpaquerytest.repository;
    import java.util.List;
    import java.util.Map;
    
    
    import org.fkit.springdatajpaquerytest.bean.Student;
    import org.springframework.data.jpa.repository.JpaRepository;
    import org.springframework.data.jpa.repository.Modifying;
    import org.springframework.data.jpa.repository.Query;
    import org.springframework.data.repository.query.Param;
    
    
    public interface StudentRepository extends JpaRepository<Student, Integer> {
        
        /**
         * 根据班级名称查询这个班级下所有的学生信息
         * 相当于JPQL语句： select s from Student s where s.clazz.name = ?1
         * @param clazzName
         * @return
         */
        List<Student> findByClazz_name(String clazzName);
        
        /**
         * @Query写法
         * 根据班级名称查询这个班级下所有的学生信息
         * ?1此处使用的是参数的位置，代表的是第一个参数
         * 此写法与 findByClazz_name方法实现的功能完全一致
         * */
        @Query("select s from Student s where s.clazz.name = ?1")
        List<Student> findStudentsByClazzName(String clazzName);
        /**
         * 使用@Query注解的形式，查询某个班级下所有学生的姓名和性别
         * @param clazzName
         * @return
         */
        @Query("select new Map(s.name as name , s.sex as sex) "
                + "from Student s where s.clazz.name = ?1")
        List<Map<String, Object>> findNameAndSexByClazzName(String clazzName);
        
        /**
         *  使用@Query注解的形式，查询某个班级下某种性别的所有学生的姓名
         *  上面方法是用的是参数的位置来查询的，Spring Data JPA中还支持用
         *  名称来匹配查询使用格式 “:参数名称” 引用
         * @param clazzName
         * @return
         */
        @Query("select s.name from Student s "
                + "where s.clazz.name = :clazzName and s.sex = :sex ")
        List<String> findNameByClazzNameAndSex(@Param("clazzName")String clazzName , @Param("sex")char sex);
        /**
         *  使用@Query注解的形式，查询某个学生属于哪个班级
         * @param stuName
         * @return
         */
        @Query("select c.name from Clazz c inner join c.students s "
                + "where s.name = ?1 ")
        String findClazzNameByStuName(String stuName);
        /**
         * 执行更新查询，使用@Query与@Modifying可以执行更新操作
         * 例如删除牛魔王这个学生
         * */
        @Modifying
        @Query("delete from Student s where s.name = ?1")
        int deleteStuByStuName(String stuName);
    }

**八 Service层**

package org.fkit.springdatajpaquerytest.service;
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    import javax.annotation.Resource;
    import org.fkit.springdatajpaquerytest.bean.Clazz;
    import org.fkit.springdatajpaquerytest.bean.Student;
    import org.fkit.springdatajpaquerytest.repository.ClazzRepository;
    import org.fkit.springdatajpaquerytest.repository.StudentRepository;
    import org.springframework.stereotype.Service;
    import org.springframework.transaction.annotation.Transactional;
    @Service
    public class SchoolService {
        
        // 注入数据访问层接口对象
        @Resource
        private StudentRepository studentRepository;
        @Resource
        private ClazzRepository clazzRepository;
        
        @Transactional
        public void saveClazzAll(List<Clazz> clazzs) {
            clazzRepository.saveAll(clazzs);
        }
        @Transactional
        public void saveStudentAll(List<Student> students) {
            studentRepository.saveAll(students);
        }
        
        public List<Map<String, Object>> getStusByClazzName(String clazzName) {
            // 使用"_" 和 @Query查询方式结果一致
            List<Student> students = studentRepository.findByClazz_name(clazzName);
    //        List<Student> students = studentRepository.findStudentsByClazzName(clazzName);
            List<Map<String, Object>>  results = new ArrayList<>();
            // 遍历查询出的学生对象，提取姓名，年龄，性别信息
            for(Student student:students){
                Map<String , Object> stu = new HashMap<>();
                stu.put("name", student.getName());
                stu.put("age", student.getAge());
                stu.put("sex", student.getSex());
                results.add(stu);
            }
            return results;
        }
        public List<Map<String, Object>> findNameAndSexByClazzName(String clazzName) {
            return studentRepository.findNameAndSexByClazzName(clazzName);
        }
        public List<String> findNameByClazzNameAndSex(
                String clazzName, char sex) {
            return studentRepository.findNameByClazzNameAndSex(clazzName, sex);
        }
        public String findClazzNameByStuName(String stuName) {
            return studentRepository.findClazzNameByStuName(stuName);
        }
        @Transactional
        public int deleteStuByStuName(String stuName) {
            return studentRepository.deleteStuByStuName(stuName);
        }
    }

**九 测试**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 2][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 3][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 4][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 5][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70]: /images/20210724/099615f155a0408da82cdc325c642ae5.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 1]: /images/20210724/a7ab279cd9eb44d98f5dc8e97e65fbc1.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 2]: /images/20210724/84b54c0f09854b1382679ef9f68b0765.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 3]: /images/20210724/b19d3db3a9704ad7b5cff107544053bd.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 4]: /images/20210724/6b29bdf59bc342abb78e7a4ae075a1ba.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 5]: /images/20210724/b2768d8c99a64f2a9d27b2b039b3e6de.png