Springboot使用spring Data jpa

1、spring jpa简介

JPA(Java Persistence API)是Sun官方提出的Java持久化规范. 为Java开发人员提供了一种对象/关联映射工具来管理Java应用中的关系数据. 它的出现是为了简化现有的持久化开发工作和整合ORM技术. 结束各个ORM框架各自为营的局面.

JPA仅仅是一套规范,不是一套产品, 也就是说Hibernate, TopLink等是实现了JPA规范的一套产品。

Spring Data JPA是Spring基于ORM框架、JPA规范的基础上封装的一套JPA应用框架,是基于Hibernate之上构建的JPA使用解决方案,用极简的代码实现了对数据库的访问和操作,包括了增、删、改、查等在内的常用功能.

2、如何使用

maven坐标

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

常用配置

#通用数据源配置
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://xxx06/xxx?charset=utf8mb4&useSSL=false
spring.datasource.username=springboot
spring.datasource.password=springboot
# Hikari 数据源专用配置
spring.datasource.hikari.maximum-pool-size=20
spring.datasource.hikari.minimum-idle=5
# JPA 相关配置
spring.jpa.show-sql=true

配置解释

spring.jpa.show-sql=true 配置在日志中打印出执行的 SQL 语句信息。

3、程序体现

定义一个实体类

package com.example.springbootjpa.entity;
import lombok.Data;
import org.hibernate.annotations.GenericGenerator;
import javax.persistence.*;
@Entity
@Table(name = "tb_user")
@Data
public class User {
    @Id
    @GenericGenerator(name = "idGenerator", strategy = "uuid")
    @GeneratedValue(generator = "idGenerator")
    private String id;
    @Column(name = "username", unique = true, nullable = false, length = 64)
    private String username;
    @Column(name = "password", nullable = false, length = 64)
    private String password;
    @Column(name = "email", length = 64)
    private String email;
}

主键采用UUID策略 @GenericGenerator是Hibernate提供的主键生成策略注解，注意下面的@GeneratedValue（JPA注解）使用generator = “idGenerator”引用了上面的name = “idGenerator”主键生成策略。

JPA的主键策略

TABLE： 使用一个特定的数据库表格来保存主键
SEQUENCE： 根据底层数据库的序列来生成主键，条件是数据库支持序列。这个值要与generator一起使用，generator 指定生成主键使用的生成器（可能是orcale中自己编写的序列）
IDENTITY： 主键由数据库自动生成（主要是支持自动增长的数据库，如mysql）
AUTO： 主键由程序控制，也是GenerationType的默认值

dao层

package com.example.springbootjpa.repository;
import com.example.springbootjpa.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;
public interface UserRepository extends JpaRepository<User, String> {
}

继承JpaRepository，并且传入实体类和主键类型。

看一下Jpa中的类图关系

最后看一下controller中的写法

package com.example.springbootjpa.controller;

import com.example.springbootjpa.entity.User;
import com.example.springbootjpa.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.web.bind.annotation.*;
import java.util.HashMap;
import java.util.Optional;
@RestController
@RequestMapping("/users")
public class UserController {
    @Autowired
    private UserRepository userRepository;
    @PostMapping()
    public User saveUser(@RequestBody User user) {
        return userRepository.save(user);
    }
    @DeleteMapping("/{id}")
    public void deleteUser(@PathVariable("id") String userId) {
        userRepository.deleteById(userId);
    }
    @PutMapping("/{id}")
    public User updateUser(@PathVariable("id") String userId, @RequestBody User user) {
        user.setId(userId);
        return userRepository.saveAndFlush(user);
    }
    @GetMapping("/{id}")
    public User getUserInfo(@PathVariable("id") String userId) {
        Optional<User> optional = userRepository.findById(userId);
        return optional.orElseGet(User::new);
    }
    @GetMapping("/list")
    public Page<User> pageQuery(@RequestParam(value = "pageNum", defaultValue = "1") Integer pageNum,
                                @RequestParam(value = "pageSize", defaultValue = "10") Integer pageSize) {
        return userRepository.findAll(PageRequest.of(pageNum - 1, pageSize));
    }

}

4、spring jpa中的查询

4.1、方法名解析

Spring Data Jpa通过解析方法名创建查询，框架在进行方法名解析时，会先把方法名多余的前缀find…By, read…By, query…By, count…By以及get…By截取掉，然后对剩下部分进行解析，第一个By会被用作分隔符来指示实际查询条件的开始。我们可以在实体属性上定义条件，并将它们与And和Or连接起来，从而创建大量查询：

User findByUsername(String username);
List<User> findByUsernameIgnoreCase(String username);
List<User> findByUsernameLike(String username);
User findByUsernameAndPassword(String username, String password);
User findByEmail(String email);
List<User> findByEmailLike(String email);
List<User> findByIdIn(List<String> ids);
List<User> findByIdInOrderByUsername(List<String> ids);
void deleteByIdIn(List<String> ids);
Long countByUsernameLike(String username);

支持的关键字、示例及JPQL片段如下表所示：

Keyword	Sample	JPQL snippet
And	findByLastnameAndFirstname	… where x.lastname = ?1 and x.firstname = ?2
Or	findByLastnameOrFirstname	… where x.lastname = ?1 or x.firstname = ?2
Is,Equals	findByFirstname,findByFirstnameIs,findByFirstnameEquals	… where x.firstname = ?1
Between	findByStartDateBetween	… where x.startDate between ?1 and ?2
LessThan	findByAgeLessThan	… where x.age < ?1
LessThanEqual	findByAgeLessThanEqual	… where x.age <= ?1
GreaterThan	findByAgeGreaterThan	… where x.age > ?1
GreaterThanEqual	findByAgeGreaterThanEqual	… where x.age >= ?1
After	findByStartDateAfter	… where x.startDate > ?1
Before	findByStartDateBefore	… where x.startDate < ?1
IsNull	findByAgeIsNull	… where x.age is null
IsNotNull,NotNull	findByAge(Is)NotNull	… where x.age not null
Like	findByFirstnameLike	… where x.firstname like ?1
NotLike	findByFirstnameNotLike	… findByFirstnameNotLike
StartingWith	findByFirstnameStartingWith	… where x.firstname like ?1 (parameter bound with appended %)
EndingWith	findByFirstnameEndingWith	… where x.firstname like ?1 (parameter bound with prepended %)
Containing	findByFirstnameContaining	… where x.firstname like ?1 (parameter bound wrapped in %)
OrderBy	findByAgeOrderByLastnameDesc	… where x.age = ?1 order by x.lastname desc
Not	findByLastnameNot	… where x.lastname <> ?1
In	findByAgeIn(Collection ages)	… where x.age in ?1
NotIn	findByAgeNotIn(Collection ages)	… where x.age not in ?1
True	findByActiveTrue()	… where x.active = true
False	findByActiveFalse()	… where x.active = false
IgnoreCase	findByFirstnameIgnoreCase	… where UPPER(x.firstame) = UPPER(?1)

4.2、自定义查询

@Query 注解的使用非常简单，只需在声明的方法上面标注该注解，同时提供一个 JPQL 查询语句即可。

@Query("select u from User u where u.email = ?1")
User getByEmail(String eamil);

@Query("select u from User u where u.username = ?1 and u.password = ?2")
User getByUsernameAndPassword(String username, String password);

@Query("select u from User u where u.username like %?1%")
List<User> getByUsernameLike(String username);

使用命名参数Using Named Parameters

默认情况下，Spring Data JPA使用基于位置的参数绑定，如前面所有示例中所述。这使得查询方法在重构参数位置时容易出错。要解决此问题，可以使用@Param注解为方法参数指定具体名称并在查询中绑定名称，如以下示例所示：

@Query("select u from User u where u.id = :id")
User getById(@Param("id") String userId);

@Query("select u from User u where u.username = :username or u.email = :email")
User getByUsernameOrEmail(@Param("username") String username, @Param("email") String email);

4.3、使用spel

从Spring Data JPA release 1.4开始，Spring Data JPA支持名为entityName的变量。它的用法是select x from #{#entityName} x。 entityName的解析方式如下：如果实体类在@Entity注解上设置了name属性，则使用它。否则，使用实体类的简单类名。为避免在@Query注解使用实际的实体类名，就可以使用#{#entityName}进行代替。如以上示例中，@Query注解的查询字符串里的User都可替换为#{#entityName}。

@Query("select u from #{#entityName} u where u.email = ?1")
User getByEmail(String eamil);

4.4、自定义修改删除

单独使用@Query注解只是查询，如涉及到修改、删除则需要再加上@Modifying注解，如：

@Transactional()
@Modifying
@Query("update User u set u.password = ?2 where u.username = ?1")
int updatePasswordByUsername(String username, String password);

@Transactional()
@Modifying
@Query("delete from User where username = ?1")
void deleteByUsername(String username);

4.5、表关系描述

多对对

package com.example.springbootjpa.entity;
import lombok.Data;
import org.hibernate.annotations.GenericGenerator;
import javax.persistence.*;
import java.util.Date;
import java.util.Set;
import java.util.UUID;
@Entity
@Table(name = "tb_user")
@Data
public class User {
    @Id
    @GenericGenerator(name = "idGenerator", strategy = "uuid")
    @GeneratedValue(generator = "idGenerator")
    private String id;
    @Column(name = "username", unique = true, nullable = false, length = 64)
    private String username;
    @Column(name = "password", nullable = false, length = 64)
    private String password;
    @Column(name = "email", unique = true, length = 64)
    private String email;
    @ManyToMany(targetEntity = Role.class, cascade = {CascadeType.PERSIST, CascadeType.MERGE}, fetch = FetchType.LAZY)
    @JoinTable(name = "tb_user_role", joinColumns = {@JoinColumn(name = "user_id", referencedColumnName = "id")},
            inverseJoinColumns = {@JoinColumn(name = "role_id", referencedColumnName = "id")})
    private Set<Role> roles;
}

package com.example.springbootjpa.entity;
import lombok.Data;
import org.hibernate.annotations.GenericGenerator;
import javax.persistence.*;
@Entity
@Table(name = "tb_role")
@Data
public class Role {
    @Id
    @GenericGenerator(name = "idGenerator", strategy = "uuid")
    @GeneratedValue(generator = "idGenerator")
    private String id;
    @Column(name = "role_name", unique = true, nullable = false, length = 64)
    private String roleName;
}

@Test
public void findByIdTest() {
    Optional<User> optional = userRepository.findById("40289f0c65674a930165674d54940000");
    Set<Role> roles = optional.get().getRoles();
    System.out.println(optional.get());
}

这块注意配置懒加载

spring:
  jpa:
    open-in-view: true
    properties:
      hibernate:
        enable_lazy_load_no_trans: true

一对多

package com.example.springbootjpa.entity;
import lombok.Data;
import org.hibernate.annotations.GenericGenerator;
import javax.persistence.*;
import java.util.Set;
@Entity
@Table(name = "tb_dept")
@Setter
@Getter
public class Department {
    @Id
    @GenericGenerator(name = "idGenerator", strategy = "uuid")
    @GeneratedValue(generator = "idGenerator")
    private String id;
    @Column(name = "dept_name", unique = true, nullable = false, length = 64)
    private String deptName;
    @OneToMany(mappedBy = "department", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private Set<Employee> employees;
}

package com.example.springbootjpa.entity;
import lombok.Data;
import org.hibernate.annotations.GenericGenerator;
import javax.persistence.*;
import java.util.UUID;
@Entity
@Table(name = "tb_emp")
@Setter
@Getter
public class Employee {
    @Id
    @GenericGenerator(name = "idGenerator", strategy = "uuid")
    @GeneratedValue(generator = "idGenerator")
    private String id;
    @Column(name = "emp_name", nullable = false, length = 64)
    private String empName;
    @Column(name = "emp_job", length = 64)
    private String empJob;
    @Column(name = "dept_id", insertable = false, updatable = false)
    private String deptId;
    @ManyToOne(targetEntity = Department.class, cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name = "dept_id")
    private Department department;
}

@Test
public void findByIdTest() {
    Optional<Employee> optional = employeeRepository.findById("93fce66c1ef340fa866d5bd389de3d79");
    System.out.println(optional.get());
}

注意，使用@Data会出现问题。

5、spring data jpa的审计功能

一般数据库表在设计时都会添加4个审计字段，Spring Data Jpa同样支持审计功能。Spring Data提供了@CreatedBy，@LastModifiedBy，@CreatedDate，@LastModifiedDate4个注解来记录表中记录的创建及修改信息。

package com.example.springbootjpa.entity;

import lombok.Data;
import org.hibernate.annotations.GenericGenerator;
import org.springframework.data.annotation.CreatedBy;
import org.springframework.data.annotation.CreatedDate;
import org.springframework.data.annotation.LastModifiedBy;
import org.springframework.data.annotation.LastModifiedDate;
import org.springframework.data.jpa.domain.support.AuditingEntityListener;

import javax.persistence.*;
import java.util.Date;
import java.util.Set;

@Entity
@EntityListeners(AuditingEntityListener.class)
@Table(name = "tb_user")
@Data
public class User {
    @Id
    @GenericGenerator(name = "idGenerator", strategy = "uuid")
    @GeneratedValue(generator = "idGenerator")
    private String id;
    @Column(name = "username", unique = true, nullable = false, length = 64)
    private String username;
    @Column(name = "password", nullable = false, length = 64)
    private String password;
    @Column(name = "email", unique = true, length = 64)
    private String email;
    @ManyToMany(targetEntity = Role.class, cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinTable(name = "tb_user_role", joinColumns = {@JoinColumn(name = "user_id", referencedColumnName = "id")},
            inverseJoinColumns = {@JoinColumn(name = "role_id", referencedColumnName = "id")})
    private Set<Role> roles;
    @CreatedDate
    @Column(name = "created_date", updatable = false)
    private Date createdDate;
    @CreatedBy
    @Column(name = "created_by", updatable = false, length = 64)
    private String createdBy;
    @LastModifiedDate
    @Column(name = "updated_date")
    private Date updatedDate;
    @LastModifiedBy
    @Column(name = "updated_by", length = 64)
    private String updatedBy;
}

实体类上还添加了@EntityListeners(AuditingEntityListener.class)，而AuditingEntityListener是由Spring Data Jpa提供的。

实现AuditorAware接口，光添加了4个审计注解还不够，得告诉程序到底是谁在创建和修改表记录

package com.example.springbootjpa.auditing;
import org.springframework.data.domain.AuditorAware;
import org.springframework.stereotype.Component;
import java.util.Optional;
@Component
public class AuditorAwareImpl implements AuditorAware<String> {
    @Override
    public Optional<String> getCurrentAuditor() {
        return Optional.of("admin");
    }
}

5.1、启动jpa的审计功能

package com.example.springbootjpa;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.jpa.repository.config.EnableJpaAuditing;
@SpringBootApplication
@EnableJpaAuditing
public class SpringBootJpaApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootJpaApplication.class, args);
    }
}

6、备注

spring data jpa官方地址： https://docs.spring.io/spring-data/jpa/docs/current/reference/html/

更多版本文档可以查阅，https://docs.spring.io/spring-data/。

希罗卡

Springboot使用spring Data jpa

Springboot使用spring Data jpa

1、spring jpa简介

2、如何使用

3、程序体现

4、spring jpa中的查询

4.1、方法名解析

4.2、自定义查询

4.3、使用spel

4.4、自定义修改删除

4.5、表关系描述

5、spring data jpa的审计功能

5.1、启动jpa的审计功能

6、备注

Search

欢迎添加我的个人微信号

Table of Contents

Springboot使用spring Data jpa

Springboot使用spring Data jpa

1、spring jpa简介

2、如何使用

3、程序体现

4、spring jpa中的查询

4.1、方法名解析

4.2、自定义查询

4.3、使用spel

4.4、自定义修改 删除

4.5、表关系描述

5、spring data jpa的审计功能

5.1、启动jpa的审计功能

6、备注

Search

欢迎添加我的个人微信号

Table of Contents

4.4、自定义修改删除