long mode 分页_在Spring Boot中使用Spring-data-jpa实现分页查询（转）

在我们平时的工作中，查询列表在我们的系统中基本随处可见，那么我们如何使用jpa进行多条件查询以及查询列表分页呢？下面我将介绍两种多条件查询方式。

1、引入起步依赖

org.springframework.boot

spring-boot-starter-web

org.springframework.boot

spring-boot-starter-thymeleaf

org.springframework.boot

spring-boot-starter-data-jpa

2、对thymeleaf和jpa进行配置

打开application.yml，添加以下参数，以下配置在之前的文章中介绍过，此处不做过多说明

spring:

thymeleaf:

cache:truecheck-template-location: truecontent-type: text/html

enabled:trueencoding: utf-8mode: HTML5

prefix: classpath:/templates/suffix: .html

excluded-view-names:

template-resolver-order:

datasource:

driver-class-name: com.mysql.jdbc.Driver

url: jdbc:mysql://localhost:3306/restful?useUnicode=true&characterEncoding=UTF-8&useSSL=false

username: root

password: root

initialize:trueinit-db: truejpa:

database: mysql

show-sql: truehibernate:

ddl-auto: update

naming:

strategy: org.hibernate.cfg.ImprovedNamingStrategy

3、编写实体Bean

@Entity

@Table(name="book")

public class Book {

@Id

@GeneratedValue(strategy = GenerationType.IDENTITY)

@Column(name = "id", updatable = false)

private Long id;

@Column(nullable = false,name = "name")

private String name;

@Column(nullable = false,name = "isbn")

private String isbn;

@Column(nullable = false,name = "author")

private String author;

public Book (String name,String isbn,String author){

this.name = name;

this.isbn = isbn;

this.author = author;

}

public Book(){

}

//此处省去get、set方法

}

public class BookQuery {

private String name;

private String isbn;

private String author;

//此处省去get、set方法

}

4、编写Repository接口

@Repository("bookRepository")

public interface BookRepository extends JpaRepository

,JpaSpecificationExecutor {

}

此处继承了两个接口，后续会介绍为何会继承这两个接口

5、抽象service层

首先抽象出接口

public interface BookQueryService {

Page findBookNoCriteria(Integer page,Integer size);

Page findBookCriteria(Integer page,Integer size,BookQuery bookQuery);

}

实现接口

@Service(value="https://my.oschina.net/wangxincj/blog/bookQueryService")

public class BookQueryServiceImpl implements BookQueryService {

@Resource

BookRepository bookRepository;

@Override

public Page findBookNoCriteria(Integer page,Integer size) {

Pageable pageable = new PageRequest(page, size, Sort.Direction.ASC, "id");

return bookRepository.findAll(pageable);

}

@Override

public Page findBookCriteria(Integer page, Integer size, final BookQuery bookQuery) {

Pageable pageable = new PageRequest(page, size, Sort.Direction.ASC, "id");

Page bookPage = bookRepository.findAll(new Specification(){

@Override

public Predicate toPredicate(Root root, CriteriaQuery> query, CriteriaBuilder criteriaBuilder) {

List list = new ArrayList();

if(null!=bookQuery.getName()&&!"".equals(bookQuery.getName())){

list.add(criteriaBuilder.equal(root.get("name").as(String.class), bookQuery.getName()));

}

if(null!=bookQuery.getIsbn()&&!"".equals(bookQuery.getIsbn())){

list.add(criteriaBuilder.equal(root.get("isbn").as(String.class), bookQuery.getIsbn()));

}

if(null!=bookQuery.getAuthor()&&!"".equals(bookQuery.getAuthor())){

list.add(criteriaBuilder.equal(root.get("author").as(String.class), bookQuery.getAuthor()));

}

Predicate[] p = new Predicate[list.size()];

return criteriaBuilder.and(list.toArray(p));

}

},pageable);

return bookPage;

}

此处我定义了两个接口，findBookNoCriteria是不带查询条件的，findBookCriteria是带查询条件的。在此处介绍一下上面提到的自定义Repository继承的两个接口，如果你的查询列表是没有查询条件，只是列表展示和分页，只需继承JpaRepository接口即可，但是如果你的查询列表是带有多个查询条件的话则需要继承JpaSpecificationExecutor接口，这个接口里面定义的多条件查询的方法。当然不管继承哪个接口，当你做分页查询时，都是需要调用findAll方法的，这个方法是jap定义好的分页查询方法。

findBookCriteria方法也可以使用以下方法实现，大家可以自行选择

@Override

public Page findBookCriteria(Integer page, Integer size, final BookQuery bookQuery) {

Pageable pageable = new PageRequest(page, size, Sort.Direction.ASC, "id");

Page bookPage = bookRepository.findAll(new Specification(){

@Override

public Predicate toPredicate(Root root, CriteriaQuery> query, CriteriaBuilder criteriaBuilder) {

Predicate p1 = criteriaBuilder.equal(root.get("name").as(String.class), bookQuery.getName());

Predicate p2 = criteriaBuilder.equal(root.get("isbn").as(String.class), bookQuery.getIsbn());

Predicate p3 = criteriaBuilder.equal(root.get("author").as(String.class), bookQuery.getAuthor());

query.where(criteriaBuilder.and(p1,p2,p3));

return query.getRestriction();

}

},pageable);

return bookPage;

}

6、编写Controller

针对有查询条件和无查询条件，我们分别编写一个Controller，默认每页显示5条，如下

@Controller

@RequestMapping(value = "https://my.oschina.net/queryBook")

public class BookController {

@Autowired

BookQueryService bookQueryService;

@RequestMapping("/findBookNoQuery")

public String findBookNoQuery(ModelMap modelMap,@RequestParam(value = "https://my.oschina.net/wangxincj/blog/page", defaultValue = "https://my.oschina.net/wangxincj/blog/0") Integer page,

@RequestParam(value = "https://my.oschina.net/wangxincj/blog/size", defaultValue = "https://my.oschina.net/wangxincj/blog/5") Integer size){

Page datas = bookQueryService.findBookNoCriteria(page, size);

modelMap.addAttribute("datas", datas);

return "index1";

}

@RequestMapping(value = "https://my.oschina.net/findBookQuery",method = {RequestMethod.GET,RequestMethod.POST})

public String findBookQuery(ModelMap modelMap, @RequestParam(value = "https://my.oschina.net/wangxincj/blog/page", defaultValue = "https://my.oschina.net/wangxincj/blog/0") Integer page,

@RequestParam(value = "https://my.oschina.net/wangxincj/blog/size", defaultValue = "https://my.oschina.net/wangxincj/blog/5") Integer size, BookQuery bookQuery){

Page datas = bookQueryService.findBookCriteria(page, size,bookQuery);

modelMap.addAttribute("datas", datas);

return "index2";

}

7、编写页面

首先我们编写一个通用的分页页面，新建一个叫page.html的页面

xmlns:th="http://www.thymeleaf.org"

xmlns:layout="http://www.ultraq.net.nz/thymeleaf/layout"

layout:decorator="page">