JPA查询创建顺序 [英] JPA query creation order by

问题描述

我正在尝试自己学习Spring，我打算通过创建一个博客网络应用程序来实现这一目标。我已经有了基本的博客功能，这是一个显示博客帖子的页面，以及一个提交表单的页面。显示博客帖子的页面显示了最新的博客文章，以及数据库中所有博客帖子的标题列表。

I'm trying to learn Spring on my own, and I'm planning to do that by creating a blog web app. I already have the basic blog functionality working, which is a page to display blog posts, and a page with a form to submit one. The page to display the blog posts shows the latest blog post, and a list of the titles of all the blog posts in the db.

获取博客的有序列表数据库中的帖子我首先在我的Repository接口中创建了一个sql查询。这可行，但现在我想使用我可以在界面中键入方法名称而不是硬编码的sql的功能。我在这里找到了支持的关键字： http://docs.spring.io/spring-data/jpa/docs/1.4.2.RELEASE/reference/html/jpa.repositories.html#jpa.query- methods.query-creation ，并尝试实现它。

To get an ordered list of blog posts out of the database I first created an sql query inside my Repository interface. This works, but now I want to use the functionality where I can just type the method name in the interface, instead of hardcoded sql. I found the supported keywords here: http://docs.spring.io/spring-data/jpa/docs/1.4.2.RELEASE/reference/html/jpa.repositories.html#jpa.query-methods.query-creation , and tried to implement it.

所以使用我的方法 findAllOrderByIdDesc（）我正在尝试实现与我的SQL查询相同的功能。我不确定为什么它不起作用，我认为我正确使用了关键字？

So with my method findAllOrderByIdDesc() I'm trying to achieve the same thing as with my sql query. I'm not sure why it doesn't work, I think I used the keywords correctly?

stackstrace（我不完全理解）：

引起：org.springframework.data.mapping.PropertyReferenceException：在org.springframework.data.mapping.PropertyPath找不到类型为int
的属性desc。（PropertyPath.java:75）
在org.springframework.data.mapping.PropertyPath.create（PropertyPath.java:327）
at org.springframework.data.mapping.PropertyPath.create（PropertyPath.java:307）
at org.springframework .data.mapping.PropertyPath.create（PropertyPath.java:330）
at org.springframework.data.mapping.PropertyPath.create（PropertyPath.java:353）
at org.springframework.data.mapping .PropertyPath.create（PropertyPath.java:307）
at org.springframework.data.mapping.PropertyPath.from（PropertyPath.java:271）
at org.springframework.data.mapping.PropertyPath.from （PropertyPath.java:245）
在org.springframework.data.repository.query.parser.Part。（Part.java:72）
at org.springframework.data.repository.query.parser.PartTree $ OrPart。（PartTree.java:188）
at org.springframework.data.repository.query.parser.PartTree $ Predicate.buildTree（PartTree.java:277）
at org.springframework.data.repository.query.parser.PartTree $ Predicate。 （PartTree.java:257）
at org.springframework.data.repository.query.parser.PartTree。（PartTree.java:71）
at org.springframework.data.jpa.repository.query。 PartTreeJpaQuery。（PartTreeJpaQuery.java:57）
at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy $ CreateQueryLookupStrategy.resolveQuery（JpaQueryLookupStrategy.java:90）
at org.springframework.data.jpa .repository.query.JpaQueryLookupStrategy $ CreateIfNotFoundQueryLookupStrategy.resolveQuery（JpaQueryLookupStrategy.java:162）
at org.springframework.data.jpa.repository.query.JpaQueryLookupStrate gy $ AbstractQueryLookupStrategy.resolveQuery（JpaQueryLookupStrategy.java:68）
at org.springframework.data.repository.core.support.RepositoryFactorySupport $ QueryExecutorMethodInterceptor。（RepositoryFactorySupport.java:290）
at org.springframework.data .repository.core.support.RepositoryFactorySupport.getRepository（RepositoryFactorySupport.java:158）
at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.getObject（RepositoryFactoryBeanSupport.java:162）
at org .springframework.data.repository.core.support.RepositoryFactoryBeanSupport.getObject（RepositoryFactoryBeanSupport.java:44）
at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean（FactoryBeanRegistrySupport.java:144）
... 32更多

The stackstrace (which I don't fully understand):
Caused by: org.springframework.data.mapping.PropertyReferenceException: No property desc found for type int at org.springframework.data.mapping.PropertyPath.(PropertyPath.java:75) at org.springframework.data.mapping.PropertyPath.create(PropertyPath.java:327) at org.springframework.data.mapping.PropertyPath.create(PropertyPath.java:307) at org.springframework.data.mapping.PropertyPath.create(PropertyPath.java:330) at org.springframework.data.mapping.PropertyPath.create(PropertyPath.java:353) at org.springframework.data.mapping.PropertyPath.create(PropertyPath.java:307) at org.springframework.data.mapping.PropertyPath.from(PropertyPath.java:271) at org.springframework.data.mapping.PropertyPath.from(PropertyPath.java:245) at org.springframework.data.repository.query.parser.Part.(Part.java:72) at org.springframework.data.repository.query.parser.PartTree$OrPart.(PartTree.java:188) at org.springframework.data.repository.query.parser.PartTree$Predicate.buildTree(PartTree.java:277) at org.springframework.data.repository.query.parser.PartTree$Predicate.(PartTree.java:257) at org.springframework.data.repository.query.parser.PartTree.(PartTree.java:71) at org.springframework.data.jpa.repository.query.PartTreeJpaQuery.(PartTreeJpaQuery.java:57) at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:90) at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateIfNotFoundQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:162) at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$AbstractQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:68) at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.(RepositoryFactorySupport.java:290) at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:158) at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.getObject(RepositoryFactoryBeanSupport.java:162) at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.getObject(RepositoryFactoryBeanSupport.java:44) at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:144) ... 32 more

我的存储库界面：

public interface PostRepository extends CrudRepository<Post, Integer> {

@Query("select p from Post p order by p.id desc")
Iterable<Post> findLastFirst();

Iterable<Post> findAllOrderByIdDesc();

}

我的邮政实体：

@Entity
public class Post {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private int id;
private Date date;
private String title;
@Lob
private String body;

protected Post() {
    date = new Date();
}

public Post(String title, String body) {
    this.date = new Date();
    this.title = title;
    this.body = body;
}

public int getId() {
    return id;
}

public String getTitle() {
    return title;
}

public void setTitle(String title) {
    this.title = title;
}

public Date getDate() {
    return date;
}

public String getBody() {
    return body;
}

public void setBody(String body) {
    this.body = body;
}

推荐答案

CrudRepository有一个扩展名名为 PagingAndSortingRepository

There is an extension to CrudRepository called PagingAndSortingRepository

 public interface PostRepository extends PagingAndSortingRepository<Post, Integer> {}

然后只需调用.findAll（new Sort（Sort.Direction.DESC，id）） ）;而不是findAllOrderByIdDesc（）;

Then just call .findAll(new Sort(Sort.Direction.DESC, "id")); instead of findAllOrderByIdDesc();

这篇关于JPA查询创建顺序的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！