Spring Boot Data JPA 排序教程 · ZetCode 中文系列教程

# Spring Boot Data JPA 排序教程 > 原文： [http://zetcode.com/springboot/datajpasort/](http://zetcode.com/springboot/datajpasort/) Spring Boot Data JPA 排序教程展示了如何在 Spring Data JPA 中对查询结果进行排序。查询结果使用`ORDER BY`子句或`Sort`对象进行排序。 Spring 是流行的 Java 应用框架，而 Spring Boot 是 Spring 的演进，可以帮助轻松地创建独立的，生产级的基于 Spring 的应用。 ## Spring Data JPA Spring Data JPA 是伞式 Spring Data 项目的一部分，该项目使实现基于 JPA 的存储库更加容易。 Spring Data JPA 使用 JPA 将数据存储在关系数据库中。它可以在运行时从存储库接口自动创建存储库实现。 ## Spring Data JPA 排序在 Spring Data JPA 中，查询结果可以通过两种方式排序： * 在 JPQL 查询中使用`ORDER BY`子句 * 将类型为`Sort`的参数添加到查询方法 ## Spring Boot Data JPA 排序示例以下应用检索按升序排序的城市。 ```java pom.xml src ├───main │ ├───java │ │ └───com │ │ └───zetcode │ │ │ Application.java │ │ ├───controller │ │ │ MyController.java │ │ ├───model │ │ │ City.java │ │ ├───repository │ │ │ CityRepository.java │ │ └───service │ │ CityService.java │ │ ICityService.java │ └───resources │ application.properties │ data-h2.sql │ schema-h2.sql └───test └───java ``` 这是项目结构。 `pom.xml` ```java <?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> <groupId>com.zetcode</groupId> <artifactId>springbootdatajpasort</artifactId> <version>1.0-SNAPSHOT</version> <packaging>jar</packaging> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>11</maven.compiler.source> <maven.compiler.target>11</maven.compiler.target> </properties> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.1.1.RELEASE</version> </parent> <dependencies> <dependency> <groupId>com.h2database</groupId> <artifactId>h2</artifactId> <scope>runtime</scope> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project> ``` 这是 Maven `pom.xml`文件。 `resources/application.properties` ```java spring.main.banner-mode=off spring.datasource.platform=h2 spring.jpa.hibernate.ddl-auto=none ``` 在主属性文件中，我们使用`spring.main.banner-mode`属性关闭 Spring Boot 横幅。 `spring.datasource.platform`设置为`h2`，因此数据库名称存在于数据库初始化脚本中。由于我们从 SQL 代码初始化脚本，因此通过将`spring.jpa.hibernate.ddl-auto`设置为`none`可以关闭从实体自动创建表的功能。 `com/zetcode/model/City.java` ```java package com.zetcode.model; import java.util.Objects; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.Table; @Entity @Table(name = "cities") public class City { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; private String name; private int population; public City() { } public City(String name, int population) { this.name = name; this.population = population; } public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getPopulation() { return population; } public void setPopulation(int population) { this.population = population; } @Override public int hashCode() { int hash = 7; hash = 79 * hash + Objects.hashCode(this.id); hash = 79 * hash + Objects.hashCode(this.name); hash = 79 * hash + this.population; return hash; } @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (obj == null) { return false; } if (getClass() != obj.getClass()) { return false; } final City other = (City) obj; if (this.population != other.population) { return false; } if (!Objects.equals(this.name, other.name)) { return false; } return Objects.equals(this.id, other.id); } @Override public String toString() { var builder = new StringBuilder(); builder.append("City{id=").append(id).append(", name=") .append(name).append(", population=") .append(population).append("}"); return builder.toString(); } } ``` 这是`City`实体。 `resources/schema-h2.sql` ```java CREATE TABLE cities(id INT PRIMARY KEY AUTO_INCREMENT, name VARCHAR(255), population INT); ``` 启动应用时，将执行`schema-h2.sql`脚本。它创建一个新的数据库表。 `resources/data-h2.sql` ```java INSERT INTO cities(name, population) VALUES('Bratislava', 432000); INSERT INTO cities(name, population) VALUES('Budapest', 1759000); INSERT INTO cities(name, population) VALUES('Prague', 1280000); INSERT INTO cities(name, population) VALUES('Warsaw', 1748000); INSERT INTO cities(name, population) VALUES('Los Angeles', 3971000); INSERT INTO cities(name, population) VALUES('New York', 8550000); INSERT INTO cities(name, population) VALUES('Edinburgh', 464000); INSERT INTO cities(name, population) VALUES('Suzhou', 4327066); INSERT INTO cities(name, population) VALUES('Zhengzhou', 4122087); INSERT INTO cities(name, population) VALUES('Berlin', 3671000); ``` 之后，执行`data-h2.sql`文件。它用数据填充表。 `com/zetcode/service/ICityService.java` ```java package com.zetcode.service; import com.zetcode.model.City; import java.util.List; public interface ICityService { List<City> findAllOrderByPopulationAsc(); List<City> findAllOrderByNameAsc(); } ``` `ICityService`包含两种签约方法。 `com/zetcode/service/CityService.java` ```java package com.zetcode.service; import com.zetcode.model.City; import com.zetcode.repository.CityRepository; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.data.domain.Sort; import org.springframework.stereotype.Service; import java.util.List; @Service public class CityService implements ICityService { @Autowired private CityRepository repository; @Override public List<City> findAllOrderByPopulationAsc() { return repository.findAllOrderByPopulationAsc(); } @Override public List<City> findAllOrderByNameAsc() { var sort = new Sort(Sort.Direction.ASC, "name"); return repository.findAllOrderByNameAsc(sort); } } ``` 在这里，我们有两种排序方法的实现。 ```java @Override public List<City> findAllOrderByNameAsc() { var sort = new Sort(Sort.Direction.ASC, "name"); return repository.findAllOrderByNameAsc(sort); } ``` `Sort`对象按名称升序对查询结果进行排序。 `Sort`作为参数传递给方法。 `com/zetcode/repository/CityRepository.java` ```java package com.zetcode.repository; import com.zetcode.model.City; import org.springframework.data.domain.Sort; import org.springframework.data.jpa.repository.Query; import org.springframework.data.repository.CrudRepository; import org.springframework.stereotype.Repository; import java.util.List; @Repository public interface CityRepository extends CrudRepository<City, Long> { @Query("FROM City ORDER BY population ASC") List<City> findAllOrderByPopulationAsc(); @Query("FROM City") List<City> findAllOrderByNameAsc(Sort sort); } ``` `CityRepository`有两种分类方法。在第一种情况下，我们使用`ORDER BY`子句。在第二种情况下，我们使用`Sort`对象。 `com/zetcode/controller/MyController.java` ```java package com.zetcode.controller; import com.zetcode.model.City; import com.zetcode.service.ICityService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; import java.util.List; @RestController public class MyController { @Autowired private ICityService cityService; @GetMapping(value = "/cities") public List<City> getCitiesByPopulation() { return cityService.findAllOrderByPopulationAsc(); } @GetMapping(value = "/cities2") public List<City> getCitiesByName() { return cityService.findAllOrderByNameAsc(); } } ``` 控制器为 RESTFul，并以 JSON 格式返回数据。 `com/zetcode/Application.java` ```java package com.zetcode; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } } ``` `Application`是设置 Spring Boot 应用的入口点。我们使用`mvn -q spring-boot:run`运行该应用。 ```java $ curl localhost:8080/cities [{"id":1,"name":"Bratislava","population":432000},{"id":7,"name":"Edinburgh","population":464000}, {"id":3,"name":"Prague","population":1280000},{"id":4,"name":"Warsaw","population":1748000}, {"id":2,"name":"Budapest","population":1759000},{"id":10,"name":"Berlin","population":3671000}, {"id":5,"name":"LosAngeles","population":3971000},{"id":9,"name":"Zhengzhou","population":4122087}, {"id":8,"name":"Suzhou","population":4327066},{"id":6,"name":"NewYork","population":8550000}] ``` 在此输出中，城市按人口按升序排序。 ```java $ curl localhost:8080/cities2 [{"id":10,"name":"Berlin","population":3671000},{"id":1,"name":"Bratislava","population":432000}, {"id":2,"name":"Budapest","population":1759000},{"id":7,"name":"Edinburgh","population":464000}, {"id":5,"name":"LosAngeles","population":3971000},{"id":6,"name":"NewYork","population":8550000}, {"id":3,"name":"Prague","population":1280000},{"id":8,"name":"Suzhou","population":4327066}, {"id":4,"name":"Warsaw","population":1748000},{"id":9,"name":"Zhengzhou","population":4122087}] ``` 在此输出中，城市按名称按升序排序。本教程展示了如何在 Spring Boot Data JPA 中对查询结果进行排序。您可能也对相关教程感兴趣： [Spring Boot Data JPA `@Query`教程](/springboot/datajpaquery/)， [Spring Boot Data JPA `@NamedQuery`教程](/springboot/datajpanamedquery/)， [Java 教程](/lang/java/)或列出[所有 Spring Boot 教程](/all/#springboot)。