java - 使用 JPA 和 Spring Boot 查询实体类型(鉴别器)

Question

我正在尝试理解 Spring Boot 和 JPA 的魔力。我有以下类(class):

基地Asset类(在我的例子中也可以是抽象的)类 Model继承自Asset .

// ASSET CLASS

import javax.persistence.DiscriminatorColumn;
import javax.persistence.DiscriminatorType;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "type", discriminatorType = DiscriminatorType.STRING)
@DiscriminatorValue(value = "asset")
public class Asset {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;
    private String name;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

还有我的模型类。

// MODEL CLASS

import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;


@Entity
@DiscriminatorValue(value = "model")
public class Model extends Asset {

    private long version;

    public long getVersion() { return version; }

    public void setVersion(long version) { this.version = version; }
}

我创建了一个存储库，我想在其中查询 findAllAssetsByType() ，但我似乎做了一些完全错误的事情。这是AssetRepository界面

//ASSET REPOSITORY

import assetservice.entity.Asset;
import java.util.List;
import org.springframework.data.jpa.repository.JpaRepository;

public interface AssetRepository extends JpaRepository<Asset, Long> {

    //big problem - store specific - if discriminiator changes this has to change too...
    //@Query("select a from Asset a where type = ?1")
    List<Asset> findAssetsByType(String type);
}

我还写了一个小测试，来说明我想要做什么:

// TEST REPOSITORY 
import static org.assertj.core.api.Assertions.assertThat;

import assetservice.core.AppLogger;
import assetservice.dao.AssetRepository;
import java.util.ArrayList;
import java.util.List;
import org.apache.logging.log4j.Logger;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@DataJpaTest
public class TestAsset {

    private static final Logger logger = AppLogger.getLogger();

    @Autowired
    private AssetRepository ar;

    @Test
    public void doSomething1() {
        Asset expected = new Asset();
        expected.setName("MyTestAsset");
        ar.save(expected);
        Asset actual = this.ar.findOne(expected.getId());
        assertThat(actual).isEqualTo(expected);
    }

    @Test
    public void doSomething2() {
        Asset expected = new Model();
        expected.setName("MyTestModel");
        ar.save(expected);
        Asset actual = this.ar.findOne(expected.getId());
        assertThat(actual).isEqualTo(expected);
    }

    @Test
    public void doSomething3() {
        Asset expectedModel = new Model();
        Asset expectedAsset = new Asset();
        expectedModel.setName("MyTestModel");
        expectedAsset.setName("MyTestAsset");
        ar.save(expectedModel);
        ar.save(expectedAsset);
        Asset actualModel = this.ar.findOne(expectedModel.getId());
        assertThat(actualModel).isEqualTo(expectedModel);

        Asset actualAsset = this.ar.findOne(expectedAsset.getId());
        assertThat(actualAsset).isEqualTo(actualAsset);

        List<Asset> expectedAssetList = new ArrayList<>();
        expectedAssetList.add(this.ar.findOne(expectedModel.getId()));
        List<Asset> actualAssetList = this.ar.findAssetsByType("model");

        logger.info("\n\n\n\n\n\n\n\n");
        logger.info(expectedAssetList);
        logger.info(actualAssetList);
        logger.info("\n\n\n\n\n\n\n\n");
    }
}

测试doSomething1和doSomething2按预期工作。测试doSomething3失败并显示

Failed to load ApplicationContext
java.lang.IllegalStateException: Failed to load ApplicationContext
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:124)
    at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:83)
    at org.springframework.boot.test.autoconfigure.SpringBootDependencyInjectionTestExecutionListener.prepareTestInstance(SpringBootDependencyInjectionTestExecutionListener.java:47)
    at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:230)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:228)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:287)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:289)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:247)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
    at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.runTestClass(JUnitTestClassExecuter.java:114)
    at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.execute(JUnitTestClassExecuter.java:57)
    at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassProcessor.processTestClass(JUnitTestClassProcessor.java:66)
    at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:51)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:32)
    at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:93)
    at com.sun.proxy.$Proxy1.processTestClass(Unknown Source)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.processTestClass(TestWorker.java:109)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:146)
    at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:128)
    at org.gradle.internal.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:404)
    at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
    at org.gradle.internal.concurrent.StoppableExecutorImpl$1.run(StoppableExecutorImpl.java:46)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
    at java.lang.Thread.run(Thread.java:748)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'assetRepository': Invocation of init method failed; nested exception is org.springframework.data.mapping.PropertyReferenceException: No property type found for type Asset!
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1628)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:742)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:303)
    at org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:120)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:98)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:116)
    ... 47 more
Caused by: org.springframework.data.mapping.PropertyReferenceException: No property type found for type Asset!
    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:247)
    at org.springframework.data.repository.query.parser.PartTree$Predicate.buildTree(PartTree.java:398)
    at org.springframework.data.repository.query.parser.PartTree$Predicate.<init>(PartTree.java:378)
    at org.springframework.data.repository.query.parser.PartTree.<init>(PartTree.java:89)
    at org.springframework.data.jpa.repository.query.PartTreeJpaQuery.<init>(PartTreeJpaQuery.java:64)
    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:436)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:221)
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.initAndReturn(RepositoryFactoryBeanSupport.java:277)
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.afterPropertiesSet(RepositoryFactoryBeanSupport.java:263)
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean.afterPropertiesSet(JpaRepositoryFactoryBean.java:101)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1687)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1624)
    ... 62 more

它似乎因Caused by: org.springframework.data.mapping.PropertyReferenceException: No property type found for type Asset!而失败。

我的问题是，在这种情况下我是否可以绕过自定义查询或 querydsl？正如你所看到的，我已经通过 @Query("select a from Asset a where type = ?1") 让它工作了，但这不是使用 Spring Boots 自动...假设我有更多 Assets 类型，在我看来，查询特定类型相当麻烦，因为我需要为我想要执行的每个查询实例化适当的实体类型，如下所示:

@Autowire
private ModelRepository mr;

...
List<Model> models = mr.findAll();

这样做会容易得多:

@Autowire
private AssetRepository ar;

...
List<Model> models = ar.findAllByType("models");

我应该使用EntityManager来查询吗？还有比 @Query 更好的方法吗？ ？我应该创建一个“ Assets ”表并使用“类型”之类的列，而不是定义所有实体吗？

Answer 1

在您的 Assets 类别中，您尚未包含列类型。因此，你的类应该看起来像这样

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private long id;
private String name;
private String type;

public long getId() {
    return id;
}

public void setId(long id) {
    this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getType() {
    return type;
}

public void setType(String type) {
    this.type = type;
}

请告诉我这是否解决了您的问题。