java - Java GraphQL 模式中的 HashMap

标签 java hashmap graphql schema

我正在尝试创建一个 GraphQL Spring Boot 应用程序以在现有 REST Web API 之上创建一个 GraphQL 层，但我在处理架构中的 HashMap 时遇到了问题。

Timeline 类有一个名为 dataReference 的字段，它是一个 HashMap。我尝试在 graphql 模式中将其定义为 DataReference 类型的列表，这是一个键/值对，但我收到以下错误:

Exception in thread "main" org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:155)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:540)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:775)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:316)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1260)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1248)
    at com.foo.bar.graphql.AppLauncher.main(AppLauncher.java:43)
Caused by: org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat
    at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize(TomcatWebServer.java:125)
    at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.<init>(TomcatWebServer.java:86)
    at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getTomcatWebServer(TomcatServletWebServerFactory.java:414)
    at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getWebServer(TomcatServletWebServerFactory.java:174)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:179)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:152)
    ... 8 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'servletRegistrationBean' defined in com.foo.bar.graphql.AppLauncher: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.web.servlet.ServletRegistrationBean]: Factory method 'servletRegistrationBean' threw exception; nested exception is com.coxautodev.graphql.tools.SchemaClassScannerError: Unable to match type definition (ListType{type=TypeName{name='DataReference'}}) with java type (java.util.Map<java.lang.String, java.lang.String>): Java class is not a List or generic type information was lost: java.util.Map<java.lang.String, java.lang.String>
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:625)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:455)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1288)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1127)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:538)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:498)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:204)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.getOrderedBeansOfType(ServletContextInitializerBeans.java:236)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.getOrderedBeansOfType(ServletContextInitializerBeans.java:224)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.addServletContextInitializerBeans(ServletContextInitializerBeans.java:100)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.<init>(ServletContextInitializerBeans.java:88)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.getServletContextInitializerBeans(ServletWebServerApplicationContext.java:250)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.selfInitialize(ServletWebServerApplicationContext.java:237)
    at org.springframework.boot.web.embedded.tomcat.TomcatStarter.onStartup(TomcatStarter.java:54)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5098)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1429)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1419)
    at java.util.concurrent.FutureTask.run$$$capture(FutureTask.java:266)
    at java.util.concurrent.FutureTask.run(FutureTask.java)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:134)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:944)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:839)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1429)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1419)
    at java.util.concurrent.FutureTask.run$$$capture(FutureTask.java:266)
    at java.util.concurrent.FutureTask.run(FutureTask.java)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:134)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:944)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:261)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:422)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:770)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.startup.Tomcat.start(Tomcat.java:370)
    at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize(TomcatWebServer.java:106)
    ... 13 more
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.web.servlet.ServletRegistrationBean]: Factory method 'servletRegistrationBean' threw exception; nested exception is com.coxautodev.graphql.tools.SchemaClassScannerError: Unable to match type definition (ListType{type=TypeName{name='DataReference'}}) with java type (java.util.Map<java.lang.String, java.lang.String>): Java class is not a List or generic type information was lost: java.util.Map<java.lang.String, java.lang.String>
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:620)
    ... 55 more
Caused by: com.coxautodev.graphql.tools.SchemaClassScannerError: Unable to match type definition (ListType{type=TypeName{name='DataReference'}}) with java type (java.util.Map<java.lang.String, java.lang.String>): Java class is not a List or generic type information was lost: java.util.Map<java.lang.String, java.lang.String>
    at com.coxautodev.graphql.tools.TypeClassMatcher.error(TypeClassMatcher.kt:22)
    at com.coxautodev.graphql.tools.TypeClassMatcher.match(TypeClassMatcher.kt:65)
    at com.coxautodev.graphql.tools.TypeClassMatcher.match(TypeClassMatcher.kt:28)
    at com.coxautodev.graphql.tools.SchemaClassScanner.scanResolverInfoForPotentialMatches(SchemaClassScanner.kt:215)
    at com.coxautodev.graphql.tools.SchemaClassScanner.scanQueueItemForPotentialMatches(SchemaClassScanner.kt:206)
    at com.coxautodev.graphql.tools.SchemaClassScanner.scanQueue(SchemaClassScanner.kt:103)
    at com.coxautodev.graphql.tools.SchemaClassScanner.scanForClasses(SchemaClassScanner.kt:81)
    at com.coxautodev.graphql.tools.SchemaParserBuilder.scan(SchemaParserBuilder.kt:149)
    at com.coxautodev.graphql.tools.SchemaParserBuilder.build(SchemaParserBuilder.kt:155)
    at com.foo.bar.graphql.AppLauncher.servletRegistrationBean(AppLauncher.java:55)
    at com.foo.bar.graphql.AppLauncher$$EnhancerBySpringCGLIB$$1ac15725.CGLIB$servletRegistrationBean$0(<generated>)
    at com.foo.bar.graphql.AppLauncher$$EnhancerBySpringCGLIB$$1ac15725$$FastClassBySpringCGLIB$$c7dabbfc.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244)
    at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:363)
    at com.foo.bar.graphql.AppLauncher$$EnhancerBySpringCGLIB$$1ac15725.servletRegistrationBean(<generated>)
    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.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
    ... 56 more

这是我的架构文件:

extend type Query {
    getFoo: Timeline
}

type Timeline {
    dataReference: [DataReference]
}

type DataReference {
    key: String
    value: String
}

还有我的模型类:

package com.foo.bar.graphql.model;

import lombok.Getter;
import lombok.Setter;

import java.util.HashMap;
import java.util.Map;

@Getter @Setter
public class Timeline {
  private Map<String, String> dataReference = new HashMap<>();
}

我找到了这个帖子 Return HashMap<String, Object> from GraphQL-Java关于在模式中定义 map 的问题。在接受的答案中，选项 1) 对我来说不可行，因为模型是从现有的 Web API 中获取的并且不能更改。上面列出了我对选项 2 的尝试，但没有奏效。我还尝试了选项 3(使用标量):

架构:

extend type Query {
    getFoo: Timeline
}

scalar Object

type Timeline {
    dataReference: Object
}

Servlet 注册:

@Bean
    public ServletRegistrationBean servletRegistrationBean() {

        GraphQLSchema schema  = SchemaParser.newParser()
                        .resolvers(fooResolver)
                        .file("graphql/foo.graphqls")
                        .scalars(ExtendedScalars.Object)
                        .build()
                        .makeExecutableSchema();
        ExecutionStrategy executionStrategy = new AsyncExecutionStrategy();
        GraphQLServlet servlet = new SimpleGraphQLServlet(schema, executionStrategy);
        ServletRegistrationBean bean = new ServletRegistrationBean(servlet, "/graphql");
        return bean;
    }

pom.xml:

<dependency>
  <groupId>com.graphql-java</groupId>
  <artifactId>graphql-java-extended-scalars</artifactId>
  <version>1.0</version>
</dependency>

但我收到此错误:Caused by: com.coxautodev.graphql.tools.SchemaClassScannerError: Expected a user-defined GraphQL scalar type with name 'Object' but found none!

如果有人可以帮助我实现它，我更喜欢在模式中包含键/值对的方法。

最佳答案

最简单的方法是使用 DTO。 使用像 mapstruct 这样的 DTO 映射器例如，将允许您自动映射除 Map 字段之外的所有字段，您将在其中应用转换。

你像这样创建一个 DTO :

@Data
@NoArgsConstructor
@AllArgsConstructor
public class TimelineDTO {

private List<DataReference> dataReference = new ArrayList();
}

获取到TimeLine对象后，将其映射到TimelineDTO，进行Map到List的转换。

List<DataReference> dataReferences = new ArrayList<>();
for (Map.Entry<String,String> entry : super.getDataReference().entrySet()) {

    dataReferences.add(new DataReference(entry.getKey(), entry.getValue()));

}

return dataReferences;

在您的 GraphQL 合约中，您改为返回 DTO:

 extend type Query {
    getFoo: TimelineDTO
}

type TimelineDTO {
    dataReference: [DataReference]
}

type DataReference {
    key: String
    value: String
}

关于java - Java GraphQL 模式中的 HashMap，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/55970945/

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