Springboot 系列 (5) - 在 Spring Boot 项目里使用 JPA 和 Thymeleaf 实现分页显示
JPA 是Java Persistence API 的简称，它是 Sun 公司在充分吸收现有ORM框架（Hibernate）的基础上，开发而来的一个Java EE 5.0 平台标准的开源的对象关系映射（ORM）规范。
Hibernate 与 JPA 的关系：
Hibernate 是一个开放源代码的对象关系映射（ORM）框架，它对 JDBC 进行了非常轻量级的对象封装，将 POJO 与 数据库表建立映射关系，是一个全自动的ORM框架，Hibernate 可以自动生成 SQL 语句，自动执行，使 Java 程序员可以方便地使用面向对象思维来操作数据库。
而 JPA 是 Sun 官方提出的 Java 持久化规范，而 JPA 是在充分吸收 Hibernate、TopLink 等 ORM 框架的基础上发展而来的。
JPA 是持久化的关系映射规范、接口 API，而 Hibernate 是其实现。
1. 开发环境
Windows版本：Windows 10 Home (20H2)
IntelliJ IDEA (https://www.jetbrains.com/idea/download/)：Community Edition for Windows 2020.1.4
Apache Maven (https://maven.apache.org/)：3.8.1
注：Spring 开发环境的搭建，可以参考 “ Spring基础知识（1）- Spring简介、Spring体系结构和开发环境配置 ”。
2. 创建 Spring Boot 基础项目
项目实例名称：SpringbootExample05
Spring Boot 版本：2.6.6
创建步骤：
(1) 创建 Maven 项目实例 SpringbootExample05；
(2) Spring Boot Web 配置；
(3) 导入 Thymeleaf 依赖包；
(4) 配置静态资源(jQuery、Bootstrap、Images)；
具体操作请参考 “Springboot 系列 (2) - 在 Spring Boot 项目里使用 Thymeleaf、JQuery+Bootstrap 和国际化” 里的项目实例 SpringbootExample02，文末包含如何使用 spring-boot-maven-plugin 插件运行打包的内容。
SpringbootExample05 和 SpringbootExample02 相比，SpringbootExample05 不包含 Thymeleaf 模版文件（templates/*.htm l）和国际化。
3. 配置数据库(MariaDB)
1) XAMPP for Windows
https://www.apachefriends.org/download.html
本文安装版本 7.4.25，用到 XAMPP 的如下功能：
+ Apache 2.4.51
+ MariaDB 10.4.21 (MySQL的分支)
+ PHP 7.4.25 (VC15 X86 64bit thread safe) + PEAR
+ phpMyAdmin 5.1.1
2) 创建数据库 springboot_example 和 product 表，SQL 脚本如下
1 CREATE TABLE `product` ( 2 `id` int(11) NOT NULL, 3 `name` varchar(50) NOT NULL, 4 `description` varchar(100) DEFAULT NULL, 5 `price` double DEFAULT NULL, 6 `createtime` timestamp NULL DEFAULT NULL 7 ) ENGINE=InnoDB DEFAULT CHARSET=utf8; 8 9 ALTER TABLE `product` ADD PRIMARY KEY (`id`); 10 11 ALTER TABLE `product` MODIFY `id` int(11) NOT NULL AUTO_INCREMENT; 12 13 INSERT INTO `product` (`id`, `name`, `description`, `price`, `createtime`) VALUES 14 (1, 'apple', 'Red apple', 7.84, '2020-01-01 01:01:01'), 15 (2, 'orange', 'Yellow orange', 11.6, '2020-02-02 02:02:02'), 16 (3, 'phone', 'Android phone', 105.30, '2020-03-03 03:03:03'), 17 (4, 'tea', 'Green tea', 6.3, '2020-04-04 04:04:04'), 18 (5, 'paper', 'White paper A4', 3.5, '2020-05-05 05:05:05'), 19 (6, 'water', 'Pure water', 1.2, '2020-06-06 06:06:06'), 20 (7, 'test1', 'Test description 1', 1.0, '2020-07-07 07:07:07'), 21 (8, 'test2', 'Test description 2', 2.0, '2020-08-08 08:08:08'), 22 (9, 'test3', 'Test description 3', 3.0, '2020-09-09 09:09:09'), 23 (10, 'test4', 'Test description 4', 4.0, '2020-10-10 10:10:10'), 24 (11, 'test5', 'Test description 5', 5.0, '2020-11-11 11:11:11'), 25 (12, 'test6', 'Test description 6', 6.0, '2020-12-12 12:12:12'), 26 (13, 'test7', 'Test description 7', 7.0, '2020-12-13 13:13:13'), 27 (14, 'test8', 'Test description 8', 8.0, '2020-12-14 14:14:14'), 28 (15, 'test9', 'Test description 9', 9.0, '2020-12-15 15:15:15'), 29 (16, 'test10', 'Test description 10', 10.0, '2020-12-16 16:16:16'), 30 (17, 'test11', 'Test description 11', 11.0, '2020-12-17 17:17:17');
注：定义表名时，不要和 SQL 的关键字同名
3）创建 src/main/java/com/example/entity/Product.java 文件
1 package com.example.entity; 2 3 import java.util.Date; 4 import javax.persistence.Column; 5 import javax.persistence.Entity; 6 import javax.persistence.Id; 7 import javax.persistence.Table; 8 import javax.persistence.GenerationType; 9 import javax.persistence.GeneratedValue; 10 11 @Entity 12 @Table(name = "product") 13 public class Product { 14 @Id 15 @GeneratedValue(strategy=GenerationType.AUTO) 16 private Integer id; 17 @Column(name = "name", length = 50) 18 private String name; 19 @Column(name = "description", length = 100) 20 private String description; 21 @Column(name = "price") 22 private Double price; 23 @Column(name = "createtime") 24 private Date createtime; 25 26 public Product() { 27 28 } 29 30 public Integer getId() { 31 return id; 32 } 33 public void setId(Integer id) { 34 this.id = id; 35 } 36 37 public String getName() { 38 return name; 39 } 40 public void setName(String name) { 41 this.name = name; 42 } 43 44 public String getDescription() { 45 return description; 46 } 47 public void setDescription(String description) { 48 this.description = description; 49 } 50 51 public Double getPrice() { 52 return price; 53 } 54 public void setPrice(Double price) { 55 this.price = price; 56 } 57 58 public Date getCreatetime() { 59 return createtime; 60 } 61 public void setCreatetime(Date createtime) { 62 this.createtime = createtime; 63 } 64 65 @Override 66 public String toString() { 67 return "Product {" + 68 "name = " + name + 69 ", description = " + description + 70 ", price = " + price + 71 ", createtime = " + createtime + 72 '}'; 73 } 74 }
4. 配置 JPA
1) 修改 pom.xml，导入 JPA 依赖包
1 <project ... > 2 ... 3 <dependencies> 4 ... 5 6 <!-- MariaDB --> 7 <dependency> 8 <groupId>org.mariadb.jdbc</groupId> 9 <artifactId>mariadb-java-client</artifactId> 10 </dependency> 11 <!-- JDBC --> 12 <dependency> 13 <groupId>org.springframework.boot</groupId> 14 <artifactId>spring-boot-starter-data-jdbc</artifactId> 15 </dependency> 16 <!-- JPA --> 17 <dependency> 18 <groupId>org.springframework.boot</groupId> 19 <artifactId>spring-boot-starter-data-jpa</artifactId> 20 </dependency> 21 22 ... 23 </dependencies> 24 25 ... 26 </project>
在IDE中项目列表 -> SpringbootExample05 -> 点击鼠标右键 -> Maven -> Reload Project
2) 修改 src/main/resources/application.properties 文件
1 spring.main.banner-mode=off 2 3 # Web server 4 server.display-name=SpringbootExample05-Test 5 server.address=localhost 6 server.port=9090 7 8 # 数据源连接信息 9 spring.datasource.driver-class-name=org.mariadb.jdbc.Driver 10 spring.datasource.url=jdbc:mysql://localhost:3306/springboot_example 11 spring.datasource.username=root 12 spring.datasource.password=123456 13 14 # JPA 相关配置 15 #spring.jpa.database-platform=org.hibernate.dialect.MySQL5InnoDBDialect 16 spring.jpa.show-sql=true 17 #spring.jpa.properties.hibernate.format_sql=true 18 #spring.jpa.hibernate.ddl-auto=update
3) 创建 src/main/java/com/example/dao/ProductJpaRepository.java 文件
1 package com.example.dao; 2 3 import org.springframework.data.jpa.repository.JpaRepository; 4 5 import com.example.entity.Product; 6 7 public interface ProductJpaRepository extends JpaRepository<Product, Integer> { 8 9 // 10 }
注：在 ProductJpaRepository 里无需重写和重载方法。
5. 视图和控制器
1) 创建 src/main/resources/templates/common.html 文件
1 <div th:fragment="header(var)"> 2 <meta charset="UTF-8"> 3 <title th:text="${var}">Title</title> 4 <link rel="stylesheet" th:href="@{/lib/bootstrap-4.2.1-dist/css/bootstrap.min.css}" href="/lib/bootstrap-4.2.1-dist/css/bootstrap.min.css"> 5 <script language="javascript" th:src="@{/lib/jquery/jquery-3.6.0.min.js}" src="/lib/jquery/jquery-3.6.0.min.js"></script> 6 <script language="javascript" th:src="@{/lib/bootstrap-4.2.1-dist/js/bootstrap.min.js}" src="/lib/bootstrap-4.2.1-dist/js/bootstrap.min.js"></script> 7 </div> 8 9 <div th:fragment="content-header" class="container" id="content-header-id"> 10 <nav class="navbar navbar-light bg-light"> 11 <a class="navbar-brand" href="#"> 12 <img th:src="@{/images/bootstrap-solid.svg}" src="/images/bootstrap-solid.svg" width="30" height="30" class="d-inline-block align-top" alt=""> 13 Thymeleaf Demo 14 </a> 15 16 <a class="nav-link" th:href="@{/logout}" th:if="${session.loginUser} != null">Logout</a> 17 </nav> 18 </div> 19 20 <div th:fragment="content-footer(var)" class="container" id="content-footer-id"> 21 <p th:text="${var}">Content Footer</p> 22 </div>
2) 创建 src/main/resources/templates/product/index.html 文件
1 <!DOCTYPE html> 2 <html lang="en" xmlns:th="http://www.thymeleaf.org"> 3 <head th:include="common::header(var='Product Index')"> 4 </head> 5 <body> 6 <div th:replace="common::content-header"></div> 7 8 <div class="container" id="content" th:style="'min-height: 480px; padding: 10px;'"> 9 <h4>Product Index Page</h4> 10 11 <p> </p> 12 <div class="alert alert-info" role="alert" th:text="${message}" th:if ="${message} != null"></div> 13 14 <table class="table table-bordered"> 15 <thead> 16 <tr> 17 <th scope="col">#</th> 18 <th scope="col">Name</th> 19 <th scope="col">Description</th> 20 <th scope="col">Price</th> 21 <th scope="col">Create Time</th> 22 </tr> 23 </thead> 24 <tbody th:if="${pageData} != null"> 25 <tr th:each="row:${pageData}" > 26 <td th:object="${row}" th:text="*{id}"></td> 27 <td th:object="${row}" th:text="*{name}"></td> 28 <td th:object="${row}" th:text="*{description}"></td> 29 <td th:object="${row}" th:text="*{price}"></td> 30 <td th:object="${row}" th:text="*{createtime}"></td> 31 </tr> 32 </tbody> 33 <tbody th:if ="${pageData} == null"> 34 <tr> 35 <td colspan="5">No record</td> 36 </tr> 37 </tbody> 38 </table> 39 40 <nav aria-label="Page navigation example" th:if="${pageData.getTotalPages() gt 1}"> 41 <ul class="pagination justify-content-end"> 42 43 <li th:if="${pageData.hasPrevious()}" class="page-item"> 44 <a th:href="@{/product?index=1}" href="/product?index=1" class="page-link"><<</a> 45 </li> 46 <li th:if="${pageData.hasPrevious()}" class="page-item"> 47 <a th:href="@{/product?index={v}&step={s}(v=${pageData.getNumber()},s=${pageData.getSize()})}" href="/product?index=&step=" class="page-link"><</a> 48 </li> 49 50 <li th:unless="${pageData.hasPrevious()}" class="page-item disabled"><a href="#" class="page-link"><<</a></li> 51 <li th:unless="${pageData.hasPrevious()}" class="page-item disabled"><a href="#" class="page-link"><</a></li> 52 53 <li th:if="${pageData.getTotalPages() le 7}" th:each="i:${#numbers.sequence(1, pageData.getTotalPages())} " th:class="${i eq pageData.getNumber()+1}?'page-item active':'page-item'"> 54 <a th:href="@{/product?index={v}&step={s}(v=${i}, s=${pageData.getSize()})}" href="/product?index=&step=" th:text="${i}" class="page-link"></a> 55 </li> 56 57 <li th:if="${pageData.getTotalPages() gt 7}" th:each="i:${#numbers.sequence(1, 3)}" th:class="${i eq pageData.getNumber()+1}?'page-item active':'page-item'"> 58 <a th:href="@{/product?index={v}&step={s}(v=${i}, s=${pageData.getSize()})}" href="/product?index=&step=" th:text="${i}" class="page-link"></a> 59 </li> 60 <li th:if="${pageData.getTotalPages() gt 7}" th:class="'page-item disabled'"> 61 <a href="#" class="page-link">...</a> 62 </li> 63 <li th:if="${pageData.getTotalPages() gt 7}" th:each="i:${#numbers.sequence(pageData.getTotalPages()-2, pageData.getTotalPages())}" th:class="${i eq pageData.getNumber()+1}?'page-item active':'page-item'"> 64 <a th:href="@{/product?index={v}&step={s}(v=${i}, s=${pageData.getSize()})}" href="/product?index=&step=" th:text="${i}" class="page-link"></a> 65 </li> 66 67 <li th:if="${pageData.hasNext()}" class="page-item"> 68 <a th:href="@{/product?index={v}&step={s}(v=${pageData.getNumber()+2},s=${pageData.getSize()})}" href="/product?index=&step=" class="page-link">></a> 69 </li> 70 <li th:if="${pageData.hasNext()}" class="page-item"> 71 <a th:href="@{/product?index={v}(v=${pageData.getTotalPages()})}" href="/product?index=" class="page-link">>></a> 72 </li> 73 74 <li th:unless="${pageData.hasNext()}" class="page-item disabled"><a href="#" class="page-link">></a></li> 75 <li th:unless="${pageData.hasNext()}" class="page-item disabled"><a href="#" class="page-link">>></a></li> 76 77 </ul> 78 </nav> 79 80 </div> 81 82 <div th:replace="common::content-footer(var='Copyright © 2020')"></div> 83 84 <script type="text/javascript"> 85 $(document).ready(function(){ 86 console.log("jQuery is running"); 87 }); 88 </script> 89 </body> 90 </html>
注：本示例，页数小于等于 7 时，显示全部页码。大于 7 时，只显示前3个页码和后3个页码，其余用省略号替代。
3) 创建 src/main/java/com/example/controller/ProductController.java 文件
1 package com.example.controller; 2 3 import javax.servlet.http.HttpServletRequest; 4 5 import org.springframework.beans.factory.annotation.Autowired; 6 import org.springframework.ui.Model; 7 import org.springframework.stereotype.Controller; 8 import org.springframework.web.bind.annotation.RequestMapping; 9 import org.springframework.web.bind.annotation.RequestMethod; 10 import org.springframework.util.StringUtils; 11 12 import org.springframework.data.domain.Page; 13 import org.springframework.data.domain.PageRequest; 14 import org.springframework.data.domain.Pageable; 15 import org.springframework.data.domain.Sort; 16 17 import com.example.entity.Product; 18 import com.example.dao.ProductJpaRepository; 19 20 @Controller 21 public class ProductController { 22 @Autowired 23 private ProductJpaRepository productJpaRepository; 24 25 @RequestMapping(value = "/product", method = RequestMethod.GET) 26 public String product(HttpServletRequest request, Model model) { 27 28 Integer index = 1; 29 Integer step = 5; 30 String strIndex = request.getParameter("index"); 31 if (StringUtils.hasText(strIndex)) { 32 index = Integer.valueOf(strIndex); 33 if (index < 1) 34 index = 1; 35 } 36 String strStep = request.getParameter("step"); 37 if (StringUtils.hasText(strStep)) { 38 step = Integer.valueOf(strStep); 39 if (step < 5) 40 step = 5; 41 } 42 43 Sort sort = Sort.by(Sort.Direction.ASC, "id"); 44 Pageable pageable= PageRequest.of(index-1, step, sort ); 45 Page<Product> pageData = productJpaRepository.findAll(pageable); 46 47 model.addAttribute("pageData", pageData); 48 49 return "product/index"; 50 } 51 }
注：PageRequest 的 page 参数是从 0 开始的，所以 index-1，对应 pageData.getNumber() 取到的当前页也是从 0 开始的。
运行并访问 http://localhost:9090/product
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示例代码：https://gitee.com/slksm/public-codes/tree/master/demos/springboot-series/SpringbootExample05
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