Sprinboot中使用JPA及简单的原生分页组件

Posted 2021-12-19 kingstar718

一、POM.xml文件配置

 

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>

　　

 

二、相关代码

 

实体:

 

@Entity
@Table(name = "userinfo")
public class UserInfo implements Serializable 
    @Id
    @GeneratedValue
    private long userid;
    private String username;
    private String password;
    private int age;
    省略getter&setter

　　

 

DAO: 仅需要继承JpaRepository, 也可以继承PagingAndSortingRepository 实现更多功能, 这里只做最简单的演示

public interface UserInfoDao extends JpaRepository<UserInfo, Long>, Serializable 
 

 

Service:

public interface UserInfoService 
    //分页查询
    Page<UserInfo> findByPage(Pageable pageable);

 

ServiceImpl:

@Service
@Transactional
public class UserInfoServiceImpl implements UserInfoService 
    @Override
    public Page<UserInfo> findByPage(Pageable pageable) 
        return userInfoDao.findAll(pageable);
    

 

Controller:

Pageable定义了很多方法，但其核心的信息只有两个：一是分页的信息（page、size(limit)），二是排序的信息。Spring Data Jpa提供了PageRequest的具体实现，Spring MVC提供了对Spring Data JPA非常好的支持，我们只提供分页以及排序信息即可：

//分页
@RequestMapping("/list")
public String pageUser(@RequestParam(value = "start", defaultValue = "0") Integer start,
                       @RequestParam(value = "limit", defaultValue = "10") Integer limit,
                       Model model)
    start = start <0 ? 0:start;
    Sort sort = new Sort(Sort.DEFAULT_DIRECTION, "userid");
    Pageable pageable = new PageRequest(start, limit, sort);
    Page<UserInfo>  page = userInfoService.findByPage(pageable);
    model.addAttribute("page", page);
    return "user/userlist";

//分页json
@RequestMapping("/pagejson")
@ResponseBody
public Page<UserInfo> pageUser(@PageableDefault(value = 15, sort = "userid", direction = Sort.Direction.ASC)Pageable pageable)
    return userInfoService.findByPage(pageable);

 

三、返回Json及对象

 

返回一个Json格式的Pageable方便查看对象:

    "content": [
        
            "userid": 1,
            "username": "sasa",
            "password": "e",
            "age": 123
        ,
        
            "userid": 11,
            "username": "问问",
            "password": "w",
            "age": 121
        
    ],
    "pageable": 
        "sort": 
            "sorted": true,
            "unsorted": false,
            "empty": false
        ,
        "offset": 0,
        "pageSize": 15,
        "pageNumber": 0,
        "paged": true,
        "unpaged": false
    ,
    "totalElements": 16,
    "totalPages": 2,
    "last": false,
    "number": 0,
    "size": 15,
    "sort": 
        "sorted": true,
        "unsorted": false,
        "empty": false
    ,
    "numberOfElements": 15,
    "first": true,
    "empty": false

 

Json显示了Pageable的相关属性;, 也可直接使用,

这里我使用的是thymeleaf模板, 于是我使用第一个controller来渲染模板, 核心的显示数据如下, 省略了前后的引入.

 

<table class="table table-hover">
    <thead>
    <tr>
        <th>id</th>
        <th>name</th>
        <th>password</th>
        <th>age</th>
        <th>details</th>
        <th>操作</th>
    </tr>
    </thead>
    <tbody>
    <tr th:each="user: $page.content">
        <th scope="row" th:text="$user.getUserid()">2</th>
        <th th:text="$user.getUsername()">leo</th>
        <th th:text="$user.getPassword()">pwd</th>
        <th th:text="$user.getAge()">13</th>
        <th><a th:href="@/user/findById(id=$user.getUserid())" >查看</a></th>  <!--代码中未给出实现,可删除或自己实现-->
        <th><a th:href="@/user/deleteById(id=$user.getUserid())" >删除</a></th>    <!--代码中未给出实现,可删除或自己实现-->
    </tr>
    </tbody>
</table>
<ul class="list-group">
    <li class="list-group-item">
        <a  class="btn-default" th:href="@/user/list(start=0)">[首页]</a>  
        <a  class="btn-default" th:if="$not page.isFirst()" th:href="@/user/list(start=$page.number-1)">[上页]</a>  
        <a  class="btn-default" th:if="$not page.isLast()" th:href="@/user/list(start=$page.number+1)">[下页]</a>  
        <a  class="btn-default" th:href="@/user/list(start=$page.totalPages-1)">[末页]</a>
    </li>
</ul>

 

 

 四、参考其他

 

另可参考这篇文章:  https://www.tianmaying.com/tutorial/spring-jpa-page-sort(整合Spring Data JPA与Spring MVC: 分页和排序)

详细介绍了PagingAndSortingRepository, Pageable对象等, 但是只返回了Json数据, 而我使用了Thymeleaf返回对象并解析, 更快实现前端.