来自JPararePository接口的查询

Question

这个问题是关于一个Spring MVC项目的，在这个项目中，我确实将Hibernate与JPA一起使用。对于消息是一个实体类

import java.io.Serializable;
import java.time.LocalDate;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Entity
@Table(name = "StoredMessage")
public class StoredMessage implements Serializable{

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long messageId;
    @Column(nullable = false)
    private Long userId;
    @Column(nullable = false)
    private String message;
    @Column(nullable = false)
    private LocalDate date;
    @ManyToOne
    private User user;

    public StoredMessage() {
       super();
    }

   public StoredMessage(Long messageId, Long userId, String message, LocalDate date) {
      super();
      this.messageId = messageId;
      this.userId = userId;
      this.message = message;
      this.date = date;
  }

  public Long getMessageId() {
      return messageId;
  }

  public void setId(Long messageId) {
      this.messageId = messageId;
  }

  public Long getUserId() {
      return userId;
  }

  public void setUserId(Long userId) {
      this.userId = userId;
  }

  public String getMessage() {
      return message;
  }

  public void setMessage(String message) {
      this.message = message;
  }

  public LocalDate getDate() {
      return date;
  }

  public void setDate(LocalDate date) {
      this.date = date;
  }

}

为了执行一些简单的查询，使用了一个从JPararePository派生的接口。

import org.springframework.data.jpa.repository.JpaRepository;

import free.oauth.model.StoredMessage;

public interface MessageRepository extends JpaRepository<StoredMessage,  Long> {

    public void saveStoredMessage(StoredMessage message);

    public void delete(Long MessageId);

    public boolean findByMessageId(Long mesageId);

    public StoredMessage findStoredMessageByMessageId(Long mesageId);

    public boolean update(StoredMessage mesage);
}

通过运行project its获取错误，如

Caused by: org.springframework.data.mapping.PropertyReferenceException: No property saveStoredMessage found for type StoredMessage!
at org.springframework.data.mapping.PropertyPath.<init>(PropertyPath.java:77)
at org.springframework.data.mapping.PropertyPath.create(PropertyPath.java:329)
at org.springframework.data.mapping.PropertyPath.create(PropertyPath.java:309)
at org.springframework.data.mapping.PropertyPath.from(PropertyPath.java:272)
at org.springframework.data.mapping.PropertyPath.from(PropertyPath.java:243)
at org.springframework.data.repository.query.parser.Part.<init>(Part.java:76)
at org.springframework.data.repository.query.parser.PartTree$OrPart.<init>(PartTree.java:235)
at org.springframework.data.repository.query.parser.PartTree$Predicate.buildTree(PartTree.java:373)
at org.springframework.data.repository.query.parser.PartTree$Predicate.<init>(PartTree.java:353)
at org.springframework.data.repository.query.parser.PartTree.<init>(PartTree.java:84)
at org.springframework.data.jpa.repository.query.PartTreeJpaQuery.<init>(PartTreeJpaQuery.java:63)
at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:103)
at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateIfNotFoundQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:214)
at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$AbstractQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:77)
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.<init>(RepositoryFactorySupport.java:435)
at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:220)
at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.initAndReturn(RepositoryFactoryBeanSupport.java:266)
at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.afterPropertiesSet(RepositoryFactoryBeanSupport.java:252)
at org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean.afterPropertiesSet(JpaRepositoryFactoryBean.java:92)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1637)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1574)
... 56 more

这种接口有什么问题，在这种类型的接口中必须遵守规则？

Answer 1

关于保存和删除，它们是开箱即用的支持，并且已经存在于界面中：

void delete(T entity)
<S extends T> S save(S entity)

这两个都定义在JpaRepository扩展的CrudRepository接口上。

关于update，在事务完成后，对查询的任何更新都将被刷新到数据库中。

如果您想要显式更新，那么试试下面的文章：How do I update an entity using spring-data-jpa？

更新

取而代之的是：

public StoredMessage findStoredMessageByMessageId(Long mesageId);

您可以使用

StoredMessage findOne(long messageId)

也来自CrudRepository接口

最后，如果您想通过某个字段而不是id来搜索唯一的实体，那么如下所示：

StoredMessage findOneStoredMessageByMessage(String message);