JavaSpring存储库生成与属性命名约定

1 月，4 周 Questions & Answers 2403

我正在使用javax.persistence和Spring，我有一个简单的实体类和一个简单的CrudRepository，在我尝试添加我自己的findByXXX()方法之前，它们工作得很好

我的实体类如下所示：

@Entity
public class Node
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column (name = "ID")
    private Integer mID;

    /** The node's activity. */
    @Column (name = "Activity", nullable = false, length = 200)
    private String mActivity;

    // ... other properties.

    public Integer getId() { return mID; }
    public void setId(Integer id) { mID = id; }
    public String getActivity() { return mActivity; }
    public void setActivity(String activity) { mActivity = activity; }
    ...
}

您会注意到我在实例属性上使用了“m”前缀的命名约定。在我添加自己的findByXXX()方法之前，这对我的存储库很有效。因此，我可以使用标准的CRUD方法从数据存储中保存和检索Node

当我尝试添加自己的查询方法时，因此：

public interface NodeRepository extends CrudRepository<Node, Integer>
{
    public List<Node> findByActivity(String activity);
}

我的系统坏了。具体来说，我的存储库的自动连接失败了（请参阅本文末尾的堆栈跟踪）。幸运的是，我发现如果我修改了我的节点类，不再在属性上使用'm'前缀，那么问题就消失了。也就是说，以下代码起作用：

@Entity
public class Node
{
    ...

    /** The node's activity. */
    @Column (name = "Activity", nullable = false, length = 200)
    private String activity;

    // ... other properties.

    public String getActivity() { return activity; }
    public void setActivity(final String activity) { this.activity = activity; }
    ...
}

当Spring构建findByActivity()方法时，它似乎是通过属性名（例如activity）而不是属性方法（例如getActivity(), setActivity()）来搜索Nodebean

有人知道情况是否如此吗？如果是这样的话，有没有办法让我保持我的命名惯例？我没有和它结婚，这只是我习惯了的事

PS：我用的是Spring3.2。x和Java 7

编辑以添加堆栈跟踪-程序正在SpringJUnit4ClassRunner:内运行

INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@32f2e8ca: defining beans [nodeRepository,org.springframework.data.repository.core.support.RepositoryInterfaceAwareBeanPostProcessor#0,org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor#0,dataSource,entityManagerFactory,transactionManager,org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.annotation.internalPersistenceAnnotationProcessor,org.springframework.context.annotation.ConfigurationClassPostProcessor.importAwareProcessor]; root of factory hierarchy
Nov 18, 2013 6:59:10 PM org.springframework.test.context.TestContextManager prepareTestInstance
SEVERE: Caught exception while allowing TestExecutionListener [org.springframework.test.context.support.DependencyInjectionTestExecutionListener@57b3fe3c] to prepare test instance [com.example.persistence.JPAXMLCfgTest@69f8421f]
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.example.persistence.JPAXMLCfgTest': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.example.persistence.NodeRepository com.example.persistence.JPAXMLCfgTest.mRepo; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'nodeRepository': FactoryBean threw exception on object creation; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:287)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1106)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireBeanProperties(AbstractAutowireCapableBeanFactory.java:374)
    at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:110)
    at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:75)
    at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:312)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:211)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:288)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:284)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:88)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
    at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:252)
    at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:141)
    at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:112)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:189)
    at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:165)
    at org.apache.maven.surefire.booter.ProviderFactory.invokeProvider(ProviderFactory.java:85)
    at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:115)
    at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:75)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.example.persistence.NodeRepository com.example.persistence.JPAXMLCfgTest.mRepo; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'nodeRepository': FactoryBean threw exception on object creation; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:513)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:92)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:284)
    ... 32 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'nodeRepository': FactoryBean threw exception on object creation; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:149)
    at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:102)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1442)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:248)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:871)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:813)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:730)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:485)
    ... 34 more
Caused by: java.lang.NullPointerException
    at org.springframework.data.jpa.repository.query.QueryUtils.isEntityPath(QueryUtils.java:462)
    at org.springframework.data.jpa.repository.query.QueryUtils.toExpressionRecursively(QueryUtils.java:445)
    at org.springframework.data.jpa.repository.query.JpaQueryCreator$PredicateBuilder.build(JpaQueryCreator.java:197)
    at org.springframework.data.jpa.repository.query.JpaQueryCreator.toPredicate(JpaQueryCreator.java:144)
    at org.springframework.data.jpa.repository.query.JpaQueryCreator.create(JpaQueryCreator.java:86)
    at org.springframework.data.jpa.repository.query.JpaQueryCreator.create(JpaQueryCreator.java:44)
    at org.springframework.data.repository.query.parser.AbstractQueryCreator.createCriteria(AbstractQueryCreator.java:109)
    at org.springframework.data.repository.query.parser.AbstractQueryCreator.createQuery(AbstractQueryCreator.java:88)
    at org.springframework.data.repository.query.parser.AbstractQueryCreator.createQuery(AbstractQueryCreator.java:73)
    at org.springframework.data.jpa.repository.query.PartTreeJpaQuery$QueryPreparer.<init>(PartTreeJpaQuery.java:98)
    at org.springframework.data.jpa.repository.query.PartTreeJpaQuery$CountQueryPreparer.<init>(PartTreeJpaQuery.java:166)
    at org.springframework.data.jpa.repository.query.PartTreeJpaQuery.<init>(PartTreeJpaQuery.java:60)
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$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.<init>(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:142)
    ... 42 more

共 (2) 个答案

# 1 楼答案

虽然我喜欢@Alan Hay的答案，但另一个选择是在解决方案中添加“服务”层。我在过去做过这件事，是为了在我的模型层中创建CRUD操作的接口

您可以使用所需的getter方法的名称创建服务类，即findByActivity，调用存储库类findByMActivity(...方法

这还允许您拥有一个包含所有可用CRUD方法的模型层，并且服务对象将只使用与该特定服务相关的CRUD操作，即ActivityService。本质上，您可以为同一数据创建多个接口，具体取决于对该数据执行的操作

然后，您的服务层类可以具有任何对用户有意义的方法名称，即findByActivity与findByActivity。Martin Fowler描述了services layer well

您的解决方案可能不需要额外的层，但它可能是一个额外的抽象，可以解决这样的接口问题，在这种情况下，更改域变量名的成本会更高
# 2 楼答案
有关如何解决查询的文档，请参见此处

http://docs.spring.io/spring-data/jpa/docs/1.4.2.RELEASE/reference/html/repositories.html#repositories.query-methods

只需简单地命名您的方法：
```
public List<Node> findByMActivity(String activity);
```
或者将映射移动到方法而不是字段，我能看到的唯一明显的方法是使用@Query实际注释这个方法，或者在这个方法将引用的其他地方定义一个命名查询
```
@Query("my custom query")
public List<Node> findByActivity(String activity);
```
要以更通用的方式执行此操作，我想您应该考虑将自定义QueryResolver重写或传递给：

org.springframework.data.jpa.repository.query.JpaQueryMethod

不管怎么说，仅仅在字段前加上“m”似乎很麻烦

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JavaSpring存储库生成与属性命名约定

共 (2) 个答案

# 1 楼答案

# 2 楼答案