corejava第10版

corejava第10版/v2ch08/bytecodeAnnotations/EntryLogger.java

@@ -0,0 +1,86 @@
+package bytecodeAnnotations;
+
+import java.io.*;
+import java.nio.file.*;
+
+import org.objectweb.asm.*;
+import org.objectweb.asm.commons.*;
+
+/**
+ * Adds "entering" logs to all methods of a class that have the LogEntry annotation.
+ * @version 1.20 2016-05-10
+ * @author Cay Horstmann
+ */
+public class EntryLogger extends ClassVisitor
+{
+   private String className;
+   
+   /**
+    * Constructs an EntryLogger that inserts logging into annotated methods of a given class.
+    * @param cg the class
+    */
+   public EntryLogger(ClassWriter writer, String className)
+   {
+      super(Opcodes.ASM5, writer);
+      this.className = className;
+   }
+   
+   @Override
+   public MethodVisitor visitMethod(int access, String methodName, String desc, 
+         String signature, String[] exceptions) 
+   {
+      MethodVisitor mv = cv.visitMethod(access,  methodName,  desc,  signature,  exceptions);   
+      return new AdviceAdapter(Opcodes.ASM5, mv, access, methodName, desc) 
+      {          
+         private String loggerName;
+          
+         public AnnotationVisitor visitAnnotation(String desc, boolean visible) 
+         {
+            return new AnnotationVisitor(Opcodes.ASM5) 
+               {
+                  public void visit(String name, Object value) 
+                  {
+                     if (desc.equals("LbytecodeAnnotations/LogEntry;") && name.equals("logger")) 
+                        loggerName = value.toString();                    
+                  }
+               };
+         }   
+          
+         public void onMethodEnter() 
+         {
+            if (loggerName != null) 
+            {
+               visitLdcInsn(loggerName);
+               visitMethodInsn(INVOKESTATIC, "java/util/logging/Logger", "getLogger", 
+                  "(Ljava/lang/String;)Ljava/util/logging/Logger;", false);
+               visitLdcInsn(className);
+               visitLdcInsn(methodName);
+               visitMethodInsn(INVOKEVIRTUAL, "java/util/logging/Logger", "entering", 
+                  "(Ljava/lang/String;Ljava/lang/String;)V", false);
+               loggerName = null;
+            }                  
+         }
+      };
+   }
+
+   /**
+    * Adds entry logging code to the given class.
+    * @param args the name of the class file to patch
+    */
+   public static void main(String[] args) throws IOException
+   {
+      if (args.length == 0)
+      {
+         System.out.println("USAGE: java bytecodeAnnotations.EntryLogger classfile");
+         System.exit(1);
+      }
+      Path path = Paths.get(args[0]);
+      ClassReader reader = new ClassReader(Files.newInputStream(path));
+      ClassWriter writer = new ClassWriter(
+         ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
+      EntryLogger entryLogger = new EntryLogger(writer, 
+         path.toString().replace(".class", "").replaceAll("[/\\\\]", "."));
+      reader.accept(entryLogger, ClassReader.EXPAND_FRAMES);
+      Files.write(Paths.get(args[0]), writer.toByteArray());
+   }   
+}