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java - 如何从对象中获取字段

问题描述

我有一堂课：

public class resultJTO extends HashMap<String, Object> {

    private static final long serialVersionUID = 1L;
}

我想获得这个 Hashmap 的特定字段。我的意思是我正在继续resultJTO

 Object airport = resultJTO.get("AIRPORT");

我试图通过这种方式做到这一点：

Object airport = resultJTO.get("AIRPORT");
        Field field = searchJTO.class.getDeclaredField("city");
        field.setAccessible(true);
        field.get(airport);

但得到

ava.lang.IllegalArgumentException: Can not set java.lang.String field AirportSearchJTO.city to java.util.HashSet

at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
at sun.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58)
at sun.reflect.UnsafeObjectFieldAccessorImpl.get(UnsafeObjectFieldAccessorImpl.java:36)
at java.lang.reflect.Field.get(Field.java:393)
at SearchServiceTest.shouldReturnProperMergedAirportIfAvailableInBothSources(SearchServiceTest.java:191)
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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.mockito.internal.runners.DefaultInternalRunner$1$1.evaluate(DefaultInternalRunner.java:44)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
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.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.mockito.internal.runners.DefaultInternalRunner$1.run(DefaultInternalRunner.java:74)
at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:80)
at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:39)
at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)

我应该怎么做才能获取例如城市？

标签： javaobject

解决方案

检查错误消息。它说：无法将 java.lang.String 字段 flightmap.service.module.search.jto.AirportSearchJTO.city 设置为 java.util.HashSet。因此它尝试将String类型的字段设置为HashSet类型的值。它不仅与错误的类型有关，而且与您想象的不同——它不是获取值，而是设置它。所以堆栈跟踪显示的东西与你想象的不同。

现在检查这一行：在 flightmap.service.module.search.SearchServiceTest.shouldReturnProperMergedAirportIfAvailableInBothSources(SearchServiceTest.java:191)

打开你的SearchServiceTest.java课程，转到第 191 行，看看那里有什么。这就是这个堆栈跟踪的原因。再说一遍：它设定价值，而不是得到它。

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