Spring注入後反射的空指標異常

自動裝配是在spring環境下當使用該類的例項時由spring容器完成了類的例項化過程，包括對依賴物件的例項化過程。

而通過反射建立例項時，是根據你呼叫的建構函式完成的例項化過程，沒有容器的自動化建立例項了，所以需要自己對依賴物件進行注入。

所以依賴spring容器例項化和自己用反射例項化是兩種獨立的方式，不能相互滲透的。

1. 異常說明

在單元測試類中，要單獨測一個類中的private方法，所以想通過反射獲得此方法，解除私有限定，然後進行呼叫。此類為Service其中注入了許多的Mapper，因此在通過呼叫此私有方法的時候報了空指標異常的錯誤，錯誤如下：

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

 

注意最後面是由NullPointerException引起的。通過Debug進去以後發現是與資料庫互動的Mapper沒有注入進來。

單元測試程式碼如下：

    @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");
    }

 

此處有個知識點：在呼叫getDeclaredMethod()獲得指定的方法時，第二個引數是方法的傳參型別，包裝類和其基本型別是不一樣，例如下面方法為boolean，如果此時在上面 cArg[1] = Boolean.class;寫為其包裝型別的話，那麼就會報錯找不到此方法的錯誤

被反射的類中方法succesExitReove ()如下

	@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();
			}
		}
	}

此處在Debug時發現tMemAcPmtDtlPoMapper為空。

2. 解決辦法

在單元測試類中@Autowired要用的Mapper，然後通過反射獲得上面方法要用到Mapper的變數，為其賦值即可

單元測試程式碼如下

    @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);
        --在此為反射的類進行賦值Mapper
        Field a1 = cls.getDeclaredField("tMemAcPmtDtlPoMapper");
        a1.setAccessible(true);
        a1.set(checkAmsPmtAndPtsFlowServiceI,tMemAcPmtDtlPoMapper);
        succesExitReove.invoke(checkAmsPmtAndPtsFlowServiceI,list,true,"1","1","2");
    }