Spring data elasticsearch 4.1

Question

升级到spring boot 2.3和spring data elasticsearch 4.0.9后的问题。我有一个这样的文档：

public class Entity implements Serializable {
    @Id private String id;
    private URL url;
    ...
}

这对于Jackson的spring data 3.0来说工作得很好，但是在升级到4.0之后，Jackson不再可用，现在我得到了一个来自spring的实例化异常，无法实例化URL对象。

例外：

org.springframework.data.mapping.model.MappingInstantiationException: Failed to instantiate java.net.URL using constructor NO_CONSTRUCTOR with arguments 
    at org.springframework.data.mapping.model.ReflectionEntityInstantiator.createInstance(ReflectionEntityInstantiator.java:65)
    at org.springframework.data.mapping.model.ClassGeneratingEntityInstantiator.createInstance(ClassGeneratingEntityInstantiator.java:87)
    at org.springframework.data.elasticsearch.core.convert.MappingElasticsearchConverter.readEntity(MappingElasticsearchConverter.java:178)
    at org.springframework.data.elasticsearch.core.convert.MappingElasticsearchConverter.readMapValue(MappingElasticsearchConverter.java:375)
    at org.springframework.data.elasticsearch.core.convert.MappingElasticsearchConverter.readValue(MappingElasticsearchConverter.java:296)
    at org.springframework.data.elasticsearch.core.convert.MappingElasticsearchConverter$ElasticsearchPropertyValueProvider.getPropertyValue(MappingElasticsearchConverter.java:915)
    at org.springframework.data.elasticsearch.core.convert.MappingElasticsearchConverter.readProperties(MappingElasticsearchConverter.java:253)
    at org.springframework.data.elasticsearch.core.convert.MappingElasticsearchConverter.readEntity(MappingElasticsearchConverter.java:185)
    at org.springframework.data.elasticsearch.core.convert.MappingElasticsearchConverter.read(MappingElasticsearchConverter.java:165)
    at org.springframework.data.elasticsearch.core.convert.MappingElasticsearchConverter.read(MappingElasticsearchConverter.java:74)
    at org.springframework.data.elasticsearch.core.AbstractElasticsearchTemplate$ReadDocumentCallback.doWith(AbstractElasticsearchTemplate.java:602)
    at org.springframework.data.elasticsearch.core.ElasticsearchRestTemplate.get(ElasticsearchRestTemplate.java:166)
    at org.springframework.data.elasticsearch.repository.support.AbstractElasticsearchRepository.findById(AbstractElasticsearchRepository.java:118)
    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.springframework.data.repository.core.support.ImplementationInvocationMetadata.invoke(ImplementationInvocationMetadata.java:72)
    at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:382)
    at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:205)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:550)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:155)
    at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:130)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:80)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:95)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
    at com.sun.proxy.$Proxy176.findById(Unknown Source)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
    at com.sun.proxy.$Proxy176.findById(Unknown Source)
    at com.callfire.starters.elasticsearch.starter.store.AbstractGenericElasticSearchMapStore.load(AbstractGenericElasticSearchMapStore.java:153)
    at com.callfire.starters.elasticsearch.starter.store.AbstractGenericElasticSearchMapStore.load(AbstractGenericElasticSearchMapStore.java:50)
    at com.hazelcast.map.impl.MapStoreWrapper.load(MapStoreWrapper.java:165)
    at com.hazelcast.map.impl.mapstore.writebehind.WriteBehindStore.load(WriteBehindStore.java:206)
    at com.hazelcast.map.impl.mapstore.writebehind.WriteBehindStore.load(WriteBehindStore.java:56)
    at com.hazelcast.map.impl.recordstore.DefaultRecordStore.putIfAbsent(DefaultRecordStore.java:1004)
    at com.hazelcast.map.impl.operation.PutIfAbsentOperation.run(PutIfAbsentOperation.java:36)
    at com.hazelcast.spi.Operation.call(Operation.java:170)
    at com.hazelcast.spi.impl.operationservice.impl.OperationRunnerImpl.call(OperationRunnerImpl.java:210)
    at com.hazelcast.spi.impl.operationservice.impl.OperationRunnerImpl.run(OperationRunnerImpl.java:199)
    at com.hazelcast.spi.impl.operationexecutor.impl.OperationThread.process(OperationThread.java:147)
    at com.hazelcast.spi.impl.operationexecutor.impl.OperationThread.process(OperationThread.java:125)
    at com.hazelcast.spi.impl.operationexecutor.impl.OperationThread.run(OperationThread.java:110)
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [java.net.URL]: No default constructor found; nested exception is java.lang.NoSuchMethodException: java.net.URL.<init>()
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:146)
    at org.springframework.data.mapping.model.ReflectionEntityInstantiator.createInstance(ReflectionEntityInstantiator.java:62)
    ... 54 common frames omitted
Caused by: java.lang.NoSuchMethodException: java.net.URL.<init>()
    at java.lang.Class.getConstructor0(Class.java:3082)
    at java.lang.Class.getDeclaredConstructor(Class.java:2178)
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:139)
    ... 55 common frames omitted

任何关于解决方案的想法都很感谢。

Answer 1

这是因为您可能没有任何以URL作为参数实例化的构造函数。

在您的例子中，构造函数应该是这样的。

public Entity(URL url, ** **) {
    this.url = url;
    **;
    **;
}

此外，你还可以使用Lombok通过@NoArgsConstructor，@AllArgsConstructor，@Data这样的注解来获得构造函数的功能。只需将其添加到你的模型类中，它就会工作。

Answer 2

从索引中的数据可以看出，URL被存储为嵌套对象url，其属性为protocol、host、port、file、authority、path、handler (本身就是一个对象)。

在读取Spring Data时，Elasticsearch尝试创建一个URL类的对象，以便在该对象上设置这些属性。但是URL类没有用于执行此操作的构造函数。

要读入该内容，您需要定义一个自定义转换器，该转换器可以读写Document对象(基本上是一个Map<String, Object>并注册该转换器(参见https://docs.spring.io/spring-data/elasticsearch/docs/4.2.5/reference/html/#elasticsearch.mapping.meta-model.conversions) )

Answer 3

长话短说。在检查旧的现有索引上的数据后，URL作为字符串存储在那里，可能是Jackson HAL模块。我能够通过添加两个转换器来保留行为。

    @ReadingConverter
public static class StringToUrlConverter implements Converter<String, URL> {
    @SneakyThrows
    @Override
    public URL convert(String url) {
        return new URL(url);
    }
}

@WritingConverter
public static class UrlToStringConverter implements Converter<URL, String> {
    @Override
    public String convert(URL url) {
        return url.toString();
    }
}