不學無數——Spring注入後反射的空指針異常

Spring注入後反射的空指針異常

1. 異常說明

在單元測試類中，要單獨測一個類中的private方法，因此想經過反射得到此方法，解除私有限定，而後進行調用。此類爲Service其中注入了許多的Mapper，所以在經過調用此私有方法的時候報了空指針異常的錯誤，錯誤以下：

java.lang.reflect.InvocationTargetException
	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 com.suixingpay.bap.service.impl.CheckAmsPmtAndPtsFlowServiceImplTest.testInvoke(CheckAmsPmtAndPtsFlowServiceImplTest.java:78)
	at com.suixingpay.bap.service.impl.CheckAmsPmtAndPtsFlowServiceImplTest.insertByList(CheckAmsPmtAndPtsFlowServiceImplTest.java:69)
	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.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
	at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252)
	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$2.evaluate(ParentRunner.java:268)
	at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
	at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: java.lang.NullPointerException
	at com.suixingpay.bap.service.impl.CheckAmsPmtAndPtsFlowServiceImpl.succesExitReove(CheckAmsPmtAndPtsFlowServiceImpl.java:247)
	... 36 more

複製代碼

注意最後面是由NullPointerException引發的。經過Debug進去之後發現是與數據庫交互的Mapper沒有注入進來。

單元測試代碼以下：

@Autowired
    private CheckAmsPmtAndPtsFlowServiceImpl checkAmsPmtAndPtsFlowServiceI;
    
    @Test
    public void insertByList()
            throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, IllegalAccessException,
            NoSuchFieldException {
        List<TBapCheckResultSave>  list = new ArrayList<>();
        Class cls = Class.forName("service.impl.CheckAmsPmtAndPtsFlowServiceImpl");
        Class[] cArg = new Class[5];
        cArg[0] = List.class;
        cArg[1] = boolean.class;
        cArg[2] = String.class;
        cArg[3] = String.class;
        cArg[4] = String.class;
        Method succesExitReove = cls.getDeclaredMethod("succesExitReove",cArg);
        succesExitReove.setAccessible(true);
        succesExitReove.invoke(checkAmsPmtAndPtsFlowServiceI,list,true,"1","1","2");
    }

複製代碼

此處有個知識點：在調用getDeclaredMethod()得到指定的方法時，第二個參數是方法的傳參類型，包裝類和其基本類型是不同，例以下面方法爲boolean，若是此時在上面 cArg[1] = Boolean.class;寫爲其包裝類型的話，那麼就會報錯找不到此方法的錯誤

被反射的類中方法succesExitReove ()以下

@Autowired
	private TMemAcPmtDtlPoMapper tMemAcPmtDtlPoMapper;
	
	private void succesExitReove(List<TBapCheckResultSave> result, boolean isFen, String sourceType, String opId, String batchId) {
		Iterator<TBapCheckResultSave> iteDownPtsNoCodeSuccces = result.iterator();
		while (iteDownPtsNoCodeSuccces.hasNext()) {
			int count;
			if (isFen) {
				count = tMemAcPmtDtlPoMapper.queryCheckFlow(bapCheckResult.getOutTransId());
			} else {
				count = tMemAcPmtDtlPoMapper.queryCheckFlow(bapCheckResult.getTransId());
			}
			bapCheckResult.setPmtCount(count);
			if (count > 0) {
				iteDownPtsNoCodeSuccces.remove();
			}
		}
	}

複製代碼

此處在Debug時發現tMemAcPmtDtlPoMapper爲空。

2. 解決辦法

在單元測試類中@Autowired要用的Mapper，而後經過反射得到上面方法要用到Mapper的變量，爲其賦值便可

單元測試代碼以下

@Autowired
    private CheckAmsPmtAndPtsFlowServiceImpl checkAmsPmtAndPtsFlowServiceI;
    --在單元測試類中進行依賴注入Mapper
    @Autowired
    private TMemAcPmtDtlPoMapper tMemAcPmtDtlPoMapper;
    
    @Test
    public void insertByList()
            throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, IllegalAccessException,
            NoSuchFieldException {
        List<TBapCheckResultSave>  list = new ArrayList<>();
        Class cls = Class.forName("service.impl.CheckAmsPmtAndPtsFlowServiceImpl");
        Class[] cArg = new Class[5];
        cArg[0] = List.class;
        cArg[1] = boolean.class;
        cArg[2] = String.class;
        cArg[3] = String.class;
        cArg[4] = String.class;
        Field a1 = cls.getDeclaredField("tMemAcPmtDtlPoMapper");
        Method succesExitReove = cls.getDeclaredMethod("succesExitReove",cArg);
        succesExitReove.setAccessible(true);
        --在此爲反射的類進行賦值Mapper
        Field a1 = cls.getDeclaredField("tMemAcPmtDtlPoMapper");
        a1.setAccessible(true);
        a1.set(checkAmsPmtAndPtsFlowServiceI,tMemAcPmtDtlPoMapper);
        succesExitReove.invoke(checkAmsPmtAndPtsFlowServiceI,list,true,"1","1","2");
    }

複製代碼