Spring Boot + Bootstrap + FreeMarker分页 (JPA, Liquibase, H2)

今天药忘吃喽~ 2023-09-26 12:11 44阅读 0赞

### 1. 引言 ###

在本文中，我们将介绍基于Spring Boot JPA、Bootstrap 和**FreeMarker的分页**组件。将数据库结果划分为页是许多应用程序中常用的功能。本教程将介绍如何使用FreeMarker模板创建一个漂亮的分页组件。

### 2. 依赖关系 ###

2.1. Maven 依赖

POC（概念证明）应用程序是使用以下依赖项作为 Maven 项目创建的：

*  [启动：弹簧启动器-启动器-web：2.1.5.发布][-_-web_2.1.5.] \- 弹簧启动 Web 启动器，
 *  [启动器：弹簧启动器-数据-jpa：2.1.5.发布][-_-jpa_2.1.5.] \- 弹簧启动数据 JPA 启动器，
 *  FreeMarker模板引擎，
 *  [组织：龙目岛：1.18.2][1.18.2] \- POJO 类的生成设置器/获取器方法，
 *  [com.h2 数据库：h2：1.4.200][com.h2 _h2_1.4.200] \- H2 数据库引擎，
 *  [组织液基：液基-核心：3.8.8][-_3.8.8] \- 管理和执行数据库更改，
 *  [org.webjars：引导：4.0.0-2][org.webjars_4.0.0-2] \- 用于引导框架的 webjar 库。

2.2. 前端库

*  Bootstrap - 用于创建响应式网站的前端框架。

项目 Maven 文件具有以下结构：`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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <artifactId>thymeleaf-bootstrap-pagination</artifactId>
    
        <properties>
            <java.version>17</java.version>
        </properties>
    
        
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.7.4</version>
            <relativePath/>
        </parent>
    
        
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-freemarker</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.liquibase</groupId>
                <artifactId>liquibase-core</artifactId>
                <version>4.16.1</version>
            </dependency>
    
            <dependency>
                <groupId>org.webjars</groupId>
                <artifactId>bootstrap</artifactId>
                <version>5.2.0</version>
            </dependency>
    
            <dependency>
                <groupId>com.h2database</groupId>
                <artifactId>h2</artifactId>
                <version>2.1.214</version>
            </dependency>
    
            <dependency>
                <groupId>org.webjars</groupId>
                <artifactId>webjars-locator</artifactId>
                <version>0.45</version>
            </dependency>
    
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>1.18.24</version>
                <scope>provided</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-devtools</artifactId>
                <scope>runtime<scope >
            </dependency>
        </dependencies>
    
        
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    
    </project>

### 3. 模型、视图、控制器层 ###

使用 **H2 数据库**和 **Liquibase** 管理数据库更改的示例应用程序。

因此，首先我们需要在`application.properties`文件中配置这些库：

spring.datasource.driver-class-name=org.h2.Driver
    spring.datasource.url=jdbc:h2:mem:testdb;MODE=PostgreSQL;DB_CLOSE_DELAY=-1
    spring.datasource.username=h2
    spring.datasource.password=pass
    
    spring.liquibase.change-log=classpath:/db-scripts/db-changelog-master.xml

在数据库层中，我们创建一个具有字段（`title`和 `body`）的`Post`实体。

package com.frontbackend.thymeleaf.bootstrap.posts.entity;
    
    import lombok.AllArgsConstructor;
    import lombok.Getter;
    import lombok.NoArgsConstructor;
    import lombok.Setter;
    
    import javax.persistence.Entity;
    import javax.persistence.Id;
    
    @Entity(name = "POSTS")
    @NoArgsConstructor
    @AllArgsConstructor
    @Setter
    @Getter
    public class Post {
    
        @Id
        private Long id;
    
        private String title;
        private String body;
    }

从`JpaRepository`扩展的数据访问对象 （`PostDAO`） 中，我们将使用采用`Pageable`参数的`findAll`方法。`Pageable` 类存储限制和排序结果记录所需的所有信息。

package com.frontbackend.thymeleaf.bootstrap.posts.control.dao;
    
    import org.springframework.data.jpa.repository.JpaRepository;
    
    import com.frontbackend.thymeleaf.bootstrap.posts.entity.Post;
    
    public interface PostDAO extends JpaRepository<Post, Long> {
    }

`PostService`类负责准备`PageRequest`类，并用`Paged`实例包装结果：

package com.frontbackend.thymeleaf.bootstrap.posts.control.service;
    
    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.stereotype.Service;
    
    import com.frontbackend.thymeleaf.bootstrap.posts.control.dao.PostDAO;
    import com.frontbackend.thymeleaf.bootstrap.posts.entity.Post;
    import com.frontbackend.thymeleaf.bootstrap.posts.entity.paging.Paged;
    import com.frontbackend.thymeleaf.bootstrap.posts.entity.paging.Paging;
    
    @Service
    public class PostService {
    
        private final PostDAO postDAO;
    
        @Autowired
        public PostService(PostDAO postDAO) {
            this.postDAO = postDAO;
        }
    
        public Paged<Post> getPage(int pageNumber, int size) {
            Sort sort = Sort.by("id");
            sort = sort.ascending();
            PageRequest request = PageRequest.of(pageNumber - 1, size, sort);
            Page<Post> postPage = postDAO.findAll(request);
            return new Paged<>(postPage, Paging.of(postPage.getTotalPages(), pageNumber, size));
        }
    }

`Paged`、`PageItem、``PageItemType` 和 `Paging`是用于准备分页组件的实用程序类。

`Paged`类具有以下结构：

package com.frontbackend.thymeleaf.bootstrap.posts.entity.paging;
    
    import org.springframework.data.domain.Page;
    
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public class Paged<T> {
    
        private Page<T> page;
    
        private Paging paging;
    
    }

`PageItem`具有以下结构：

package com.frontbackend.thymeleaf.bootstrap.posts.entity.paging;
    
    import lombok.AllArgsConstructor;
    import lombok.Builder;
    import lombok.Getter;
    import lombok.NoArgsConstructor;
    import lombok.Setter;
    
    @Setter
    @Getter
    @Builder
    @NoArgsConstructor
    @AllArgsConstructor
    public class PageItem {
    
        private PageItemType pageItemType;
    
        private int index;
    
        private boolean active;
    
    }

`PageItemType`是包含两个值的枚举：

package com.frontbackend.thymeleaf.bootstrap.posts.entity.paging;
    
    public enum PageItemType {
    
        DOTS,
        PAGE
    
    }

`Paging`类负责计算页面和点在分页组件中的显示方式：

package com.frontbackend.thymeleaf.bootstrap.posts.entity.paging;
    
    import java.util.ArrayList;
    import java.util.List;
    
    import lombok.AllArgsConstructor;
    import lombok.Builder;
    import lombok.Getter;
    import lombok.NoArgsConstructor;
    import lombok.Setter;
    
    @Setter
    @Getter
    @Builder
    @NoArgsConstructor
    @AllArgsConstructor
    public class Paging {
    
        private static final int PAGINATION_STEP = 3;
    
        private boolean nextEnabled;
        private boolean prevEnabled;
        private int pageSize;
        private int pageNumber;
    
        private List<PageItem> items = new ArrayList<>();
    
        public void addPageItems(int from, int to, int pageNumber) {
            for (int i = from; i < to; i++) {
                items.add(PageItem.builder()
                                  .active(pageNumber != i)
                                  .index(i)
                                  .pageItemType(PageItemType.PAGE)
                                  .build());
            }
        }
    
        public void last(int pageSize) {
            items.add(PageItem.builder()
                              .active(false)
                              .pageItemType(PageItemType.DOTS)
                              .build());
    
            items.add(PageItem.builder()
                              .active(true)
                              .index(pageSize)
                              .pageItemType(PageItemType.PAGE)
                              .build());
        }
    
        public void first(int pageNumber) {
            items.add(PageItem.builder()
                              .active(pageNumber != 1)
                              .index(1)
                              .pageItemType(PageItemType.PAGE)
                              .build());
    
            items.add(PageItem.builder()
                              .active(false)
                              .pageItemType(PageItemType.DOTS)
                              .build());
        }
    
        public static Paging of(int totalPages, int pageNumber, int pageSize) {
            Paging paging = new Paging();
            paging.setPageSize(pageSize);
            paging.setNextEnabled(pageNumber != totalPages);
            paging.setPrevEnabled(pageNumber != 1);
            paging.setPageNumber(pageNumber);
    
            if (totalPages < PAGINATION_STEP * 2 + 6) {
                paging.addPageItems(1, totalPages + 1, pageNumber);
    
            } else if (pageNumber < PAGINATION_STEP * 2 + 1) {
                paging.addPageItems(1, PAGINATION_STEP * 2 + 4, pageNumber);
                paging.last(totalPages);
    
            } else if (pageNumber > totalPages - PAGINATION_STEP * 2) {
                paging.first(pageNumber);
                paging.addPageItems(totalPages - PAGINATION_STEP * 2 - 2, totalPages + 1, pageNumber);
    
            } else {
                paging.first(pageNumber);
                paging.addPageItems(pageNumber - PAGINATION_STEP, pageNumber + PAGINATION_STEP + 1, pageNumber);
                paging.last(totalPages);
            }
    
            return paging;
        }
    }

**GET** 请求由`PostController`类处理。要更改当前页面和页面大小，我们需要添加两个请求参数：

*  **页码** \- 当前页码（默认第 1 页），
 *  **大小** \- 页面大小（默认为 5 行）：

package com.frontbackend.thymeleaf.bootstrap.posts.boundary;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Controller;
    import org.springframework.ui.Model;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestParam;
    
    import com.frontbackend.thymeleaf.bootstrap.posts.control.service.PostService;
    
    @Controller
    @RequestMapping("/")
    public class PostController {
    
        private final PostService postService;
    
        @Autowired
        public PostController(PostService postService) {
            this.postService = postService;
        }
    
        @GetMapping
        public String posts(@RequestParam(value = "pageNumber", required = false, defaultValue = "1") int pageNumber,
                @RequestParam(value = "size", required = false, defaultValue = "5") int size, Model model) {
            model.addAttribute("posts", postService.getPage(pageNumber, size));
            return "posts";
        }
    }

`Application`是 Java 类，其主要方法是启动Spring Boot应用程序服务器：

package com.frontbackend.thymeleaf.bootstrap;
    
    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);
        }
    }

### 4. FreeMarker模板 ###

表示层包含单个FreeMarker模板`posts.ftlh`：

`posts.ftlh`视图具有以下结构：

<!doctype html>
    <head>
        <title>Spring Boot FreeMarker Application - Bootstrap Table</title>
        <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css">
        <script src="https://code.jquery.com/jquery-3.5.1.slim.min.js"></script>
        <script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js"></script>
        <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/js/bootstrap.min.js"></script>
        <style>
            .panel-table .panel-body {
                padding: 0;
            }
    
            .panel-table .panel-body .table-bordered {
                border-style: none;
                margin: 0;
            }
    
            .panel-table .panel-body .table-bordered > thead > tr > th:first-of-type {
                text-align: center;
                width: 100px;
            }
    
            .panel-table .panel-body .table-bordered > thead > tr > th:last-of-type,
            .panel-table .panel-body .table-bordered > tbody > tr > td:last-of-type {
                border-right: 0px;
            }
    
            .panel-table .panel-body .table-bordered > thead > tr > th:first-of-type,
            .panel-table .panel-body .table-bordered > tbody > tr > td:first-of-type {
                border-left: 0px;
            }
    
            .panel-table .panel-body .table-bordered > tbody > tr:first-of-type > td {
                border-bottom: 0px;
            }
    
            .panel-table .panel-body .table-bordered > thead > tr:first-of-type > th {
                border-top: 0px;
            }
    
            .panel-table .panel-footer .pagination {
                margin: 0;
            }
    
            /*
            used to vertically center elements, may need modification if you're not using default sizes.
            */
            .panel-table .panel-footer .col {
                line-height: 34px;
                height: 34px;
            }
    
            .panel-table .panel-heading .col h3 {
                line-height: 30px;
                height: 30px;
            }
    
            .panel-table .panel-body .table-bordered > tbody > tr > td {
                line-height: 34px;
            }
    
    
        </style>
    </head>
    <body>
    
    
    <nav class="navbar navbar-expand-lg navbar-dark bg-dark static-top">
        <div class="container">
            <a class="navbar-brand" href="/">FreeMarker - Bootstrap Table</a>
            <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarResponsive"
                    aria-controls="navbarResponsive"
                    aria-expanded="false" aria-label="Toggle navigation">
                <span class="navbar-toggler-icon"></span>
            </button>
            <div class="collapse navbar-collapse" id="navbarResponsive">
                <ul class="navbar-nav ml-auto">
                    <li class="nav-item active">
                        <a class="nav-link" href="#">Home
                            <span class="sr-only">(current)</span>
                        </a>
                    </li>
                    <li class="nav-item">
                        <a class="nav-link" href="#">About</a>
                    </li>
                    <li class="nav-item">
                        <a class="nav-link" href="#">Services</a>
                    </li>
                    <li class="nav-item">
                        <a class="nav-link" href="#">Contact</a>
                    </li>
                </ul>
            </div>
        </div>
    </nav>
    <section class="h-100">
        <div class="container h-100">
            <div class="row justify-content-md-center">
                <div class="card">
                    <h1>Post CRUD operation with Freemarker Template</h1>
                    <a href="/create">Create New Post</a>
                    <table class="table">
                        <thead>
                        <tr>
                            <th scope="col">Id</th>
                            <th scope="col">Title</th>
                            <th scope="col">Body</th>
                            <th scope="col"></th>
                            <th scope="col"></th>
                        </tr>
                        </thead>
                        <tbody>
                        <#list posts.page.content as post>
                            <tr>
                                <th scope="row">${post.id}</th>
                                <td>${post.title}</td>
                                <td>${post.body}</td>
                                <td><a href="/update/${post.id}">Update</a></td>
                                <td><a href="/delete/${post.id}">Delete</a></td>
                            </tr>
                        </#list>
                        </tbody>
                    </table>
                </div>
    
            </div>
            <div class="panel-footer">
                <div class="row">
    
    
                    <div class="col col-xs-2">
                        Total items: ${posts.page.totalElements}- item ${(posts.page.number )*posts.page.size +1 } -
                        ${(posts.page.number )*posts.page.size +posts.page.numberOfElements  }
                    </div>
                    <div class="col col-xs-10">
                        <nav aria-label="Page navigation" class="paging">
                            <#if (posts.page.totalPages> 1)>
                                <ul class="pagination">
    
                                    <li class="page-item ${(posts.paging.isPrevEnabled())?string('' , 'disabled')}">
                                        <a class="page-link" href="/?pageNumber=${posts.paging.pageNumber - 1}"
                                           tabindex="-1">Previous</a>
                                    </li>
    
                                    <#list posts.paging.getItems() as item>
                                        <#if (item.pageItemType.name() == 'PAGE')>
                                            <li class="page-item ${(item.index == posts.paging.pageNumber)?string('active' , '')}">
                                                <a class="page-link" href="/?pageNumber=${item.index}">${item.index}</a>
                                            </li>
                                        </#if>
                                        <#if (item.pageItemType.name() == 'DOTS')>
                                            <li class="page-item disabled">
                                                <a class="page-link" href="#">...</a>
                                            </li>
                                        </#if>
                                    </#list>
    
    
                                    <li class="page-item ${(posts.paging.isNextEnabled())?string('' , 'disabled')}">
                                        <a class="page-link" href="/?pageNumber=${posts.paging.pageNumber + 1}"
                                        >Next</a>
                                    </li>
    
                                </ul>
                            </#if>
                        </nav>
                    </div>
    
                </div>
            </div>
    
        </div>
    </body>
    </html>

分页组件存储在导航标记中：`<nav aria-label="Page navigation" class="paging">...</nav>`。此代码可以很容易地移动到[片段中，][Link 1]但为了示例应用程序的清晰度，我们将其与表一起保存在单个文件中。

### 5. 输出 ###

正在运行的应用程序位于 URL 下，并提供以下功能：`http://locahost:8080`

![79199f63fe364fff57e34ff1902389f7.gif][]

###  ###

### ![76ca7a22455247b9a647b2c73320971a.png][] ###

### 6. 结论 ###

在本文中，我们介绍了如何基于春季JPA和**引导**框架构建**FreeMarker分页**组件。我们将弹簧启动应用程序与 **H2 内存数据库**、**JPA** 和 **Liquibase** 结合使用来创建数据库结构，并用样本 100 条记录填充它。

像往常一样，本文中使用的代码位于我们的 [https://github.com/allwaysoft/spring-boot-jpa-freemarker-bootstrap-pagination][https_github.com_allwaysoft_spring-boot-jpa-freemarker-bootstrap-pagination]下。

[-_-web_2.1.5.]: https://frontbackend.com/maven/artifact/org.springframework.boot/spring-boot-starter-web/2.1.5.RELEASE
[-_-jpa_2.1.5.]: https://frontbackend.com/maven/artifact/org.springframework.boot/spring-boot-starter-data-jpa/2.1.5.RELEASE
[1.18.2]: https://frontbackend.com/maven/artifact/org.projectlombok/lombok/1.18.2
[com.h2 _h2_1.4.200]: https://frontbackend.com/maven/artifact/com.h2database/h2/1.4.200
[-_3.8.8]: https://frontbackend.com/maven/artifact/org.liquibase/liquibase-core/3.8.8
[org.webjars_4.0.0-2]: https://frontbackend.com/maven/artifact/org.webjars/bootstrap/4.0.0-2
[Link 1]: https://frontbackend.com/thymeleaf/how-to-work-with-fragments-in-thymeleaf
[79199f63fe364fff57e34ff1902389f7.gif]: https://img-blog.csdnimg.cn/img_convert/79199f63fe364fff57e34ff1902389f7.gif
[76ca7a22455247b9a647b2c73320971a.png]: https://img-blog.csdnimg.cn/76ca7a22455247b9a647b2c73320971a.png
[https_github.com_allwaysoft_spring-boot-jpa-freemarker-bootstrap-pagination]: https://github.com/allwaysoft/spring-boot-jpa-freemarker-bootstrap-pagination