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Spring Data JPA--动态查询--Specification--使用

陈情雅雅 2022-02-25 阅读 157
spring数据库sqlhibernatejava


​

简介

​说明​

​        ​本文用实例介绍JPA如何使用Specification进行动态查询（多条件查询）。

        有时候我们在查询某个实体的时候，给定的查询条件不是固定的，这个时候就需要动态构建相应的查询语句。

        （说点其他的：jpa相比Mybatis-Plus，差太多了。学jpa完全是为了维护以前的项目，如果新建项目，一定要用Mybatis-Plus????）

​JpaSpecificationExecutor中定义的方法​

public interface JpaSpecificationExecutor<T> {
    T findOne(Specification<T> var1);

    List<T> findAll(Specification<T> var1);

    Page<T> findAll(Specification<T> var1, Pageable var2);

    List<T> findAll(Specification<T> var1, Sort var2);

    long count(Specification<T> var1);
}

​接口Specification​

可以简单理解为，Specification构造的就是查询条件。我们看看Specification中定义的方法。

/*
* root ：T表示查询对象的类型，代表查询的根对象，可以通过root获取实体中的属性
* query ：代表一个顶层查询对象，用来自定义查询
* cb ：用来构建查询，此对象里有很多条件方法
**/
public interface Specification<T> {
    Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb);
}

  2. root
  1. Root接口，主要用于处理实体和字段、实体与实体之间的关系。
  1. query
  1. CriteriaQuery接口，主要用于对查询结果的处理。包括groupBy、orderBy、having、distinct等操作。
  1. criteriaBuilder
  1. CriteriaBuilder接口，主要用于拼接各种条件、模拟sql函数等。

CriteriaBuilder接口（太多了，只截取一部分）：

Spring Data JPA--动态查询--Specification--使用_数据库

​使用​

如果你想使用这个功能，只需要继承JpaSpecificationExecutor接口。

public interface UserRepository extends CrudRepository<User, Long>, JpaSpecificationExecutor<User> {
}

公共代码

配置文件及依赖

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/jpa?characterEncoding=UTF-8&serverTimezone=Asia/Shanghai
    username: root
    password: 222333

  jpa:
    # 打印sql
    show-sql: true
    # 关闭属性的延时加载
    open-in-view: false
#    hibernate:
#      # 是否开启自动更新数据库表结构。生产中不要开启。
#      #   有以下几个值供选择。常用：update、none
#      #   create：每次加载hibernate时都删除上次生成的表，再根据你的model类生成新表。即使两次没有改变也这样执行，可能导致表数据丢失。
#      #   create-drop：每次加载hibernate时，先删除已存在的表结构再重新生成，sessionFactory一关闭，表就自动删除。
#      #   update：第一次加载hibernate时根据model类自动建立表结构，以后加载hibernate时根据model类自动更新表结构。
#      #           即使表结构变了但表中的行仍然存在不会删除以前的行。
#      #           部署到服务器后，表结构是不会被马上建立起来的，是要等应用第一次运行起来后才会。
#      #   validate：每次加载hibernate时，验证创建数据库表结构，只会和数据库中的表进行比较，不会创建新表，但是会插入新值。
#      #   none：关闭自动更新
#      ddl-auto: none
#
#      # hibernate5及之后的命名策略配置。
#      naming:
#        # 负责模型对象层次的处理，将对象模型处理为逻辑名称
#        #   有以下5个值供选择：
#        #     ImplicitNamingStrategyJpaCompliantImpl（默认值）后四者均继承自它。
#        #     ImplicitNamingStrategyComponentPathImpl
#        #     ImplicitNamingStrategyLegacyHbmImpl
#        #     ImplicitNamingStrategyLegacyJpaImpl
#        #     SpringImplicitNamingStrategy
#        implicit-strategy: org.hibernate.boot.model.naming.ImplicitNamingStrategyJpaCompliantImpl
#
#        # 映射成真实的数据名称的处理，将逻辑名称处理为物理名称。
#        #   有以下2个值供选择：
#        #     PhysicalNamingStrategyStandardImpl：直接映射，若有@Column则以其为准。等同于之前的DefaultNamingStrategy
#        #     SpringPhysicalNamingStrategy（默认值）：字段为小写，当有大写字母的时候会转换为分隔符号“_”。等同于之前的ImprovedNamingStrategy
#        physical-strategy: org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy
#
#        # hibernate5之前的命名策略配置。
#        #   有以下2个值供选择：
#        #     DefaultNamingStrategy（默认值）：直接映射，若有@Column则以其为准。
#        #     ImprovedNamingStrategy：字段为小写，当有大写字母的时候会转换为分隔符号“_”。
#        # naming-strategy: org.hibernate.cfg.ImprovedNamingStrategy

pom.xml

<?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 https://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>2.5.3</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo_jpa</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo_jpa</name>
    <description>demo_jpa</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.hibernate.javax.persistence</groupId>
            <artifactId>hibernate-jpa-2.1-api</artifactId>
            <version>1.0.2.Final</version>
        </dependency>

        <dependency>
            <groupId>com.github.xiaoymin</groupId>
            <artifactId>knife4j-spring-boot-starter</artifactId>
            <version>3.0.2</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </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>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

表结构及数据

business.sql

DROP TABLE IF EXISTS t_user;

CREATE TABLE `t_user`
(
    `id`   bigint(0) AUTO_INCREMENT,
    `user_name` VARCHAR(32),
    `age`  int,
    PRIMARY KEY (id)
) ENGINE = InnoDB;

INSERT INTO `t_user` values (1, 'Tony1', 21);
INSERT INTO `t_user` values (2, 'Tony2', 22);
INSERT INTO `t_user` values (3, 'Tony3', 23);
INSERT INTO `t_user` values (4, 'Tony3', 24);

代码

​Entity​

package com.example.demo.user.entity;

import lombok.Data;
import lombok.NoArgsConstructor;

import javax.persistence.*;

@Data
@NoArgsConstructor
@Entity
@Table(name = "t_user")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String userName;

    private Integer age;
}

​Repository​

package com.example.demo.user.repository;

import com.example.demo.user.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Query;
import org.springframework.stereotype.Repository;

@Repository
public interface UserRepository extends JpaRepository<User, Long>, JpaSpecificationExecutor<User> {

}

实例：简单查询（列表/分页）

​Controller​

package com.example.demo.user.controller;

import com.example.demo.user.entity.User;
import com.example.demo.user.repository.UserRepository;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;
import java.util.ArrayList;
import java.util.List;

@Api(tags = "动态查询（Specification）")
@RestController
@RequestMapping("/bySpecification")
public class DynamicQueryBySpecificationController {
    @Autowired
    private UserRepository userRepository;

    @ApiOperation("列表")
    @GetMapping("list")
    public void list() {
        Specification<User> specification = buildCondition1("Tony", 23);
        List<User> all = userRepository.findAll(specification);
        System.out.println(all);
    }

    @ApiOperation("分页")
    @GetMapping("page")
    public void page() {
        Specification<User> specification = buildCondition1("Tony", 23);

        Sort sort = Sort.by(Sort.Direction.DESC, "id");
        PageRequest pageRequest = PageRequest.of(0, 2, sort);

        Page<User> page = userRepository.findAll(specification, pageRequest);
        System.out.println(page.getContent());
    }

        // 通过userName和age进行查询（与的关系）
    private Specification<User> buildCondition1(String userName, Integer age) {
        //重写toPredicate方法
        return (Root<User> root, CriteriaQuery<?> query, CriteriaBuilder cb) -> {

            List<Predicate> predicateList = new ArrayList<>();

            if (StringUtils.isNotBlank(userName)) {
                // 本处我都转为小写，进行模糊匹配
                predicateList.add(cb.like(cb.lower(root.get("userName").as(String.class)),
                        "%" + userName.toLowerCase() + "%"));
            }

            if (age != null) {
                predicateList.add(cb.equal(root.get("age").as(Integer.class), age));
            }

            return cb.and(predicateList.toArray(new Predicate[0]));

            // 也可以这么写返回值，但麻烦
            // Predicate[] andPredicate = new Predicate[predicateList.size()];
            // return cb.and(predicateList.toArray(andPredicate));
        };
    }
}

​测试​

​测试列表​

访问： ​bySpecification/list">​http://localhost:8080/bySpecification/list​​

后端结果：

Hibernate: select user0_.id as id1_0_, user0_.age as age2_0_, user0_.user_name as user_nam3_0_ from t_user user0_ where (lower(user0_.user_name) like ?) and user0_.age=23
[User(id=3, userName=Tony3, age=23)]

​测试分页​

访问： ​bySpecification/page">​http://localhost:8080/bySpecification/page​​

后端结果：

Hibernate: select user0_.id as id1_0_, user0_.age as age2_0_, user0_.user_name as user_nam3_0_ from t_user user0_ where (lower(user0_.user_name) like ?) and user0_.age=23 order by user0_.id desc limit ?
[User(id=3, userName=Tony3, age=23)]

实例：复杂查询（列表）

​Controller​

package com.example.demo.user.controller;

import com.example.demo.user.entity.User;
import com.example.demo.user.repository.UserRepository;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;
import java.util.ArrayList;
import java.util.List;

@Api(tags = "动态查询（Specification）")
@RestController
@RequestMapping("/bySpecification")
public class DynamicQueryBySpecificationController {
    @Autowired
    private UserRepository userRepository;

    @ApiOperation("列表（复杂条件）")
    @GetMapping("listComplex")
    public void listComplex() {
        Specification<User> specification1 = buildCondition2(1L, "Tony", 23);
        List<User> all = userRepository.findAll(specification1);
        System.out.println(all);

        System.out.println("----------------------------------------------------------");

        Specification<User> specification2 = buildCondition2(1L, "Tony", null);
        List<User> all2 = userRepository.findAll(specification2);
        System.out.println(all2);

        System.out.println("----------------------------------------------------------");

        Specification<User> specification3 = buildCondition2(null, "Tony", 23);
        List<User> all3 = userRepository.findAll(specification3);
        System.out.println(all3);
    }

// 查找id不等于某个值 而且 userName或age满足条件的数据
    private Specification<User> buildCondition2(Long excludeId, String userName, Integer age) {
        //重写toPredicate方法
        return (Root<User> root, CriteriaQuery<?> query, CriteriaBuilder cb) -> {
            List<Predicate> predicateList = new ArrayList<>();

            if (excludeId != null) {
                Predicate idPredicate = cb.notEqual(root.get("id").as(Long.class), excludeId);
                predicateList.add(idPredicate);
            }

            // 拼接 userName或age 这个条件
            List<Predicate> userNameOrAgePredicates = new ArrayList<>();
            if (StringUtils.isNotBlank(userName)) {
                // 本处我都转为小写，进行模糊匹配
                Predicate userNamePredicate = cb.like(cb.lower(root.get("userName").as(String.class)),
                        "%" + userName.toLowerCase() + "%");
                userNameOrAgePredicates.add(userNamePredicate);
            }

            if (age != null) {
                Predicate agePredicate = cb.equal(root.get("age").as(Integer.class), age);
                userNameOrAgePredicates.add(agePredicate);
            }

            Predicate[] tmpUserNameOrAgePredicate = new Predicate[userNameOrAgePredicates.size()];
            Predicate userNameOrAgePredicate = cb.or(userNameOrAgePredicates.toArray(tmpUserNameOrAgePredicate));
            predicateList.add(userNameOrAgePredicate);

            return cb.and(predicateList.toArray(new Predicate[0]));

            // 也可以这么写返回值，但麻烦
            // Predicate[] andPredicate = new Predicate[predicateList.size()];
            // return cb.and(predicateList.toArray(andPredicate));
        };
    }
}

​ 测试​

​测试列表​

访问： ​bySpecification/listComplex">​http://localhost:8080/bySpecification/listComplex​​

后端结果：

Hibernate: select user0_.id as id1_0_, user0_.age as age2_0_, user0_.user_name as user_nam3_0_ from t_user user0_ where user0_.id<>1 and (lower(user0_.user_name) like ? or user0_.age=23)
[User(id=2, userName=Tony2, age=22), User(id=3, userName=Tony3, age=23), User(id=4, userName=Tony3, age=24)]
----------------------------------------------------------
Hibernate: select user0_.id as id1_0_, user0_.age as age2_0_, user0_.user_name as user_nam3_0_ from t_user user0_ where user0_.id<>1 and (lower(user0_.user_name) like ?)
[User(id=2, userName=Tony2, age=22), User(id=3, userName=Tony3, age=23), User(id=4, userName=Tony3, age=24)]
----------------------------------------------------------
Hibernate: select user0_.id as id1_0_, user0_.age as age2_0_, user0_.user_name as user_nam3_0_ from t_user user0_ where lower(user0_.user_name) like ? or user0_.age=23
[User(id=1, userName=Tony1, age=21), User(id=2, userName=Tony2, age=22), User(id=3, userName=Tony3, age=23), User(id=4, userName=Tony3, age=24)]

其他网址

​​SpringDataJpa中的复杂查询和动态查询，多表查询。（保姆级教程）​​

​


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