Spring Data JPA 代码架构图 spring data jpa pageable

本页将介绍使用 Spring Data JPA + MySQL 数据库进行 Spring Boot 分页和排序。当我们拥有大型数据集时，分页将提高应用程序的性能。它将数据集的较小块呈现给用户。

Spring Data JPA 提供了PagingAndSortingRepository 扩展接口CrudRepository以在 Spring Boot 应用程序中实现分页和排序。接口中声明了两个方法PagingAndSortingRepository：

1. Iterable<T> findAll(Sort sort) – 返回按给定选项排序的所有实体。
2. Page<T> findAll(Pageable pageable)– 返回满足 Pageable 对象中提供的分页限制的实体页面。

使用的技术

查找此应用程序中使用的所有技术的列表。

1. 弹簧工具套件 4
2. JDK 8
3. Spring Boot 2.1.9.RELEASE
4. Spring Data 2.1.9.RELEASE
5. MySQL 数据库
6. Maven 3

需要依赖

要在应用程序中启用分页和排序，以下依赖项必须在构建路径中。将它们添加到pom.xml。

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

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项目结构

我们在 STS 4 IDE 中的应用程序的最终项目结构将如下所示：

1. 初始设置

没有数据集，我们什么都做不了。分页和排序将应用于数据，因此第一步是创建一些虚拟数据集。在这里，我们提供了 MySQL 数据库模式。

employee.sql

CREATE DATABASE /*!32312 IF NOT EXISTS*/`websparrow` /*!40100 DEFAULT CHARACTER SET latin1 */;

/*Table structure for table `employee` */

DROP TABLE IF EXISTS `employee`;

CREATE TABLE `employee` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `email` varchar(255) DEFAULT NULL,
  `first_name` varchar(255) DEFAULT NULL,
  `last_name` varchar(255) DEFAULT NULL,
  `city` varchar(50) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `UK_fopic1oh5oln2khj8eat6ino0` (`email`)
) ENGINE=InnoDB AUTO_INCREMENT=30 DEFAULT CHARSET=latin1;

/*Data for the table `employee` */

insert  into `employee`(`id`,`email`,`first_name`,`last_name`,`city`) values (1,'[e-mail]','Sandeep','Jaiswal','New Delhi'),(2,'[e-mail]','Prince','Kumar','Mumbai'),(3,'[e-mail]','Abhinav','Rathi','New Delhi'),(17,'[e-mail]','Gaurav','Aggrawal','Mumbai'),(18,'[e-mail]','Sandeep','Sharma','Pune'),(19,'[e-mail]','Shani','Tripathi','Banglore'),(20,'[e-mail]','Ritesh','Singh','Hyderabad'),(21,'[e-mail]','Piyush','Kumar','Banglore'),(22,'[e-mail]','Sunandana','Tiwari','Kolkata'),(23,'[e-mail]','Kumkum','Singh','New Delhi'),(24,'[e-mail]','Pooja','Kumari','Pune'),(25,'[e-mail]','Naga','Reddy','Chennai'),(26,'[e-mail]','Jitendra','Upadhyay','Mumbai'),(27,'[e-mail]','Ashish','Singh','Pune'),(28,'[e-mail]','Ashutosh','Pandey','Mumbai'),
(29,'[e-mail]','Vipin','Kumar','Hyderabad');

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2. 实体

假设我们有一个Employee实体，每个员工都由id唯一标识。

Employee.java

package org.websparrow.entity;

@Entity
@Table(name = "employee")
public class Employee implements Serializable {

	private static final long serialVersionUID = 5009021772979651472L;
	@Id
	private Integer id;
	private String firstName;
	private String lastName;
	private String email;
	private String city;

	// constructor, getters, and setters
}

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2. 创建存储库

要访问Employee，我们需要EmployeeRepository扩展PagingAndSortingRepositorySpring Data 提供的 ，并在应用程序中启用分页和排序功能。您可以添加您的派生查询方法。

EmployeeRepository.java

package org.websparrow.repository;

import org.springframework.data.repository.PagingAndSortingRepository;
import org.springframework.stereotype.Repository;
import org.websparrow.entity.Employee;

@Repository
public interface EmployeeRepository
		extends PagingAndSortingRepository<Employee, Integer> {

}

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3.控制器

EmployeeController类自动装配以EmployeeRepository从数据库中获取数据并公开 REST 端点。

3.1 分页

创建一个PageRequest对象，它是Pageable接口的实现，将PageRequest对象作为参数传递给存储库方法。

我们可以PageRequest通过传入请求的页码和页面大小来创建一个对象。

注意：默认页数从零开始。

@GetMapping(value = "/employee/page/{pageNo}")
public Page<Employee> getEmployeeWithPaination(@PathVariable int pageNo) {

	/**
	 * Return the Page object containing list of 4 employees of requested
	 * page no.
	 */
	Pageable pageable = PageRequest.of(pageNo, PAGE_SIZE);
	return employeeRepository.findAll(pageable);
}

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3.2 分页和排序

同样，我们可以通过传递类的实例对分页结果进行排序Sort。

@GetMapping(value = "/employee/page/sort/{pageNo}")
public Page<Employee> getEmployeePaginatedAndSorted(
		@PathVariable int pageNo) {

	/**
	 * Return the Page object containing list of 3 employees of requested
	 * page and sorted by the first name
	 */
	Pageable pageableSortedByFirstName = PageRequest.of(pageNo, PAGE_SIZE,
			Sort.by("firstName"));

	/**
	 * Return the Page object containing list of 3 employees of requested
	 * page and sorted by the city in descending order
	 */
	Pageable pageableSortedByCityDesc = PageRequest.of(pageNo, PAGE_SIZE,
			Sort.by("city").descending());

	/**
	 * Return the Page object containing list of 3 employees of page 0 and
	 * sorted by the city in descending order and first name in ascending
	 * order
	 */
	Pageable pageableSortedByCityDescFirstNameAsc = PageRequest.of(pageNo,
			PAGE_SIZE, Sort.by("city").descending().and(Sort.by("firstName")));

	// return employeeRepository.findAll(pageableSortedByFirstName);
	
	// return employeeRepository.findAll(pageableSortedByCityDesc);
		
	return employeeRepository.findAll(pageableSortedByCityDescFirstNameAsc);
}

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3.3 排序

但是，如果我们想要排序形式的所有记录，只需传递Sortto的实例。Iterable<T> findAll(Sort sort)

@GetMapping(value = "/employee/sort")
public Iterable<Employee> getEmployeeSored() {

	/**
	 * Returns all entities sorted by the given options.
	 */
	return employeeRepository.findAll(Sort.by("lastName"));
}

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最后，完整的EmployeeController类如下所示：

EmployeeController.java

package org.websparrow.controller;

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.data.domain.Sort;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.websparrow.entity.Employee;
import org.websparrow.repository.EmployeeRepository;

@RestController
@RequestMapping("/api")
public class EmployeeController {

	private static final int PAGE_SIZE = 3;

	@Autowired
	private EmployeeRepository employeeRepository;

	@GetMapping(value = "/employee/page/{pageNo}")
	public Page<Employee> getEmployeePaginated(@PathVariable int pageNo) {

		/**
		 * Return the Page object containing list of 3 employees of requested
		 * page no.
		 */
		Pageable pageable = PageRequest.of(pageNo, PAGE_SIZE);
		return employeeRepository.findAll(pageable);
	}

	@GetMapping(value = "/employee/page/sort/{pageNo}")
	public Page<Employee> getEmployeePaginatedAndSorted(
			@PathVariable int pageNo) {

		/**
		 * Return the Page object containing list of 3 employees of requested
		 * page and sorted by the first name
		 */
		Pageable pageableSortedByFirstName = PageRequest.of(pageNo, PAGE_SIZE,
				Sort.by("firstName"));

		/**
		 * Return the Page object containing list of 3 employees of requested
		 * page and sorted by the city in descending order
		 */
		Pageable pageableSortedByCityDesc = PageRequest.of(pageNo, PAGE_SIZE,
				Sort.by("city").descending());

		/**
		 * Return the Page object containing list of 3 employees of page 0 and
		 * sorted by the city in descending order and first name in ascending
		 * order
		 */
		Pageable pageableSortedByCityDescFirstNameAsc = PageRequest.of(pageNo,
				PAGE_SIZE,
				Sort.by("city").descending().and(Sort.by("firstName")));

		// return employeeRepository.findAll(pageableSortedByFirstName);

		// return employeeRepository.findAll(pageableSortedByCityDesc);

		return employeeRepository.findAll(pageableSortedByCityDescFirstNameAsc);
	}

	@GetMapping(value = "/employee/sort")
	public Iterable<Employee> getEmployeeSored() {

		/**
		 * Returns all entities sorted by the given options.
		 */
		return employeeRepository.findAll(Sort.by("lastName"));
	}
}

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4. application.properties

在application.properties文件中配置数据库连接字符串以建立应用程序和数据库之间的连接。

application.properties

# MySQL database connection strings
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.url=jdbc:mysql://localhost:3306/websparrow

# JPA property settings
spring.jpa.hibernate.ddl-auto=update
spring.jpa.properties.hibernate.show_sql=true

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运行应用程序

该类 SpringBootPagintionApp 包含主要方法并负责启动应用程序。

SpringBootPaginationApp.java

package org.websparrow;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootPaginationApp {

	public static void main(String[] args) {
		SpringApplication.run(SpringBootPaginationApp.class, args);
	}
}

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测试应用程序

要测试应用程序，请通过执行上述类启动 Spring Boot 应用程序，并在您喜欢的 Web 浏览器中点击以下 URL：

注意：默认页数从零开始。

1. 要获取分页记录：http://localhost:8080/api/employee/page/0 其中零 (0) 是请求的页码。
2. 分页和排序记录：http://localhost:8080/api/employee/page/sort/3 其中 3 是请求的页码。
3. 排序记录：http://localhost:8080/api/employee/sort

下载源代码：spring-boot-pagination-and-sorting-using-spring-data-jpa.zip

参考

1. Spring Data 派生的 findBy 查询方法示例
2. Spring Data CrudRepository 接口示例
3. Spring Boot RESTful Web 服务示例
4. 接口 PagingAndSortingRepository