Android AspectJ实例讲解

作者: YWMZ | 来源:发表于2015-12-17 20:18 被阅读3106次

    文章目录

    • 如何织入代码
    • call vs execution
    • withincode
    • 碰到的问题

    如何织入代码

    MethedTrace.java是AspectJ代码,需要织入切面代码到MainActivity.java

    // MainActivity.java
    package org.sdet.aspectj;
    
    public class MainActivity extends Activity {
      @Override
      protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
      }  
    }
    
    // MethodTracer.java
    package org.sdet.aspectj;
    
    import android.util.Log;
    
    @Aspect
    public class MethodTracer {
    
      private static final String TAG = MethodTracer.class.getSimpleName();
    
      @Before("execution (protected void org.sdet.aspectj.MainActivity.onCreate(android.os.Bundle))")
      public void adviceOnCreate(JoinPoint joinPoint) {
        Log.v(TAG, joinPoint.toString());
      }
    }
    

    执行下面的命令行,

    java -cp <classpath> org.aspectj.tools.ajc.Main -inpath <MainActivity.class path> -aspectpath <MethodTracer.class path>
    

    新生成的MainActivity.class,用Java bytecode decompile工具打开,如下。

    import org.sdet.aspectj.MethodTracer;
    import org.aspectj.lang.JoinPoint;
    import org.aspectj.lang.JoinPoint.StaticPart;
    import org.aspectj.runtime.reflect.Factory;
    
    public class MainActivity extends Activity {
    
      private static final JoinPoint.StaticPart ajc$tjp_0;
    
      private static void ajc$preClinit() {
        Factory localFactory = new Factory("MainActivity.java", MainActivity.class);
        ajc$tjp_0 = localFactory.makeSJP("method-execution", localFactory.makeMethodSig("4", "onCreate", "org.sdet.aspectj.MainActivity", "android.os.Bundle", "savedInstanceState", "", "void"), 13);   
      }
    
      protected void onCreate(Bundle savedInstanceState) {
        Bundle localBundle = savedInstanceState;
        // BEGIN - 织入的代码
        JoinPoint localJoinPoint = Factory.makeJP(ajc$tjp_0, this, this, localBundle);
        MethodTracer.aspectOf().adviceOnCreate(localJoinPoint);
        // END - 织入的代码
        super.onCreate(savedInstanceState);
        setContentView(2130903040);
      }
    }
    

    相关API解读,

    //  org.aspectj.runtime.reflect.Factory.java
    public MethodSignature makeMethodSig(
      java.lang.String modifiers,        // public: 1, private: 2, protected: 4
      java.lang.String   methodName,     // 函数名: onCreate
      java.lang.String   declaringType,  // 类名: org.sdet.aspectj.MainActivity
      java.lang.String[] paramTypes,     // 参数类型: [android.os.Bundle, ]
      java.lang.String[] paramNames,     // 参数名: [savedInstanceState,]
      java.lang.String[] exceptionTypes, // 异常类型: ""
      java.lang.String   returnType)     // 返回类型: void
    )
    
    public JoinPoint.StaticPart makeSJP(
      java.lang.String kind,           //
      Signature sig,                   //
      int l                            // 代码行号
     )
    

    call和execution的区别

    Paste_Image.png
    // MethodTracer.java
    @Aspect
    public class MethodTracer {
    
      @Before("execution (private void org.sdet.aspectj.MainActivity.method4Execution(..))")
      public void adviceOnExecution(JoinPoint joinPoint) {
        Log.v(TAG, joinPoint.toString());
      }
    
      @Before("call (private void org.sdet.aspectj.MainActivity.method4Call(..))")
      public void adviceOnCall(JoinPoint joinPoint) {
        Log.v(TAG, joinPoint.toString());
      }
    }
    
    
    public class MainActivity extends Activity {
    
      private static final JoinPoint.StaticPart ajc$tjp_0;
      private static final JoinPoint.StaticPart ajc$tjp_1;
     
      private static void ajc$preClinit() {
        Factory localFactory = new Factory("MainActivity.java", MainActivity.class);
        ajc$tjp_0 = localFactory.makeSJP("method-call", localFactory.makeMethodSig("2", "method4Call", "org.sdet.aspectj.MainActivity", "", "", "", "void"), 16);
        ajc$tjp_1 = localFactory.makeSJP("method-execution", localFactory.makeMethodSig("2", "method4Execution", "org.sdet.aspectj.MainActivity", "", "", "", "void"), 42);
      }
    
      protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(2130903040);
        method4Execution();
        // call织入的位置
        MainActivity localMainActivity = this;
        JoinPoint localJoinPoint = Factory.makeJP(ajc$tjp_0, this, localMainActivity);
        MethodTracer.aspectOf().adviceOnCall(localJoinPoint);
        localMainActivity.method4Call();
      }
    
      private void method4Execution() {
        // execution织入的位置
        JoinPoint localJoinPoint = Factory.makeJP(ajc$tjp_1, this, this);
        MethodTracer.aspectOf().adviceOnExecution(localJoinPoint);
        System.out.println("in method method4Execution");
      }
     
      private void method4Call() {
        System.out.println("in method method4Call");
      }
    }
    

    withincode

    假设方法functionA, functionB都调用了dummy,但只想在functionB调用dummy时织入代码。

    //  MainActivity.java
    public class MainActivity extends Activity {
    
      @Override
      protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        functionA();
        functionB();
      }
    
      private void functionA() { dummy(); }
      private void functionB() { dummy(); }
      private void dummy() { }
    }
    
    // MethodTracer.java
    @Aspect
    public class MethodTracer {
      // withincode: 在functionB方法内
      @Pointcut("withincode(void org.sdet.aspectj.MainActivity.functionB(..))")
      public void invokeFunctionB() {}
    
      // call: 调用dummy方法
      @Pointcut("call(void org.sdet.aspectj.MainActivity.dummy(..))")
      public void invokeDummy() {}
    
      // 在functionB内调用dummy方法
      @Pointcut("invokeDummy() && invokeFunctionB()")
      public void invokeDummyInsideFunctionB() {}
    
      @Before("invokeDummyInsideFunctionB()")
      public void beforeInvokeDummyInsideFunctionB(JoinPoint joinPoint) {
        System.out.printf("Before.InvokeDummyInsideFunctionB.advice() called on '%s'", joinPoint);
      }
    }
    
    // MainActivity.java
    
    public class MainActivity extends Activity {
    
      private static final JoinPoint.StaticPart ajc$tjp_0;
    
      private static void ajc$preClinit() {
        Factory localFactory = new Factory("MainActivity.java", MainActivity.class);
        ajc$tjp_0 = localFactory.makeSJP("method-call", localFactory.makeMethodSig("2", "dummy", "org.sdet.aspectj.MainActivity", "", "", "", "void"), 56);
      }
    
      protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(2130903040);    
        functionA();
        functionB();
      }
    
      private void functionA() {
        dummy();
      }
    
      // 只有functionB调用dummy时才会织入代码
      private void functionB() {
        MainActivity localMainActivity = this;
        JoinPoint localJoinPoint = Factory.makeJP(ajc$tjp_0, this, localMainActivity);
        MethodTracer.aspectOf().beforeInvokeDummyInsideFunctionB(localJoinPoint);
        localMainActivity.dummy();
      }
    

    around

    AspectJ “around” and “proceed” with “before / after”

    http://stackoverflow.com/questions/18016503/aspectj-around-and-proceed-with-before-after

    碰到的问题

    • com.android.dx.cf.iface.ParseException: bad class file magic (cafebabe) or version (0034.0000)
      原因:Set compliance level to 1.8时会碰到这个异常

    • java.lang.NoSuchMethodError: org.sdet.aspectj.MethodTracer.aspectOf
      原因:AspectJ代码用了javac编译

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