Java编程的动态性， 第4部分: 用Javassist进行类转换 - 编程入门网
作者 佚名技术
来源 NET编程
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发布时间 2012-06-17
System.out.println("Added timing to method " +
argv[0] + "." + argv[1]);
}
} catch (CannotCompileException ex) {
ex.printStackTrace();
} catch (NotFoundException ex) {
ex.printStackTrace();
} catch (IOException ex) {
ex.printStackTrace();
}
} else {
System.out.println("Usage: JassistTiming class method- name");
}
}
private static void addTiming(CtClass clas, String mname)
throws NotFoundException, CannotCompileException {
// get the method information (throws exception if method with
// given name is not declared directly by this class, returns
// arbitrary choice if more than one with the given name)
CtMethod mold = clas.getDeclaredMethod(mname);
// rename old method to synthetic name, then duplicate the
// method with original name for use as interceptor
String nname = mname+"$impl";
mold.setName(nname);
CtMethod mnew = CtNewMethod.copy(mold, mname, clas, null);
// start the body text generation by saving the start time
// to a local variable, then call the timed method; the
// actual code generated needs to depend on whether the
// timed method returns a value
String type = mold.getReturnType().getName();
StringBuffer body = new StringBuffer();
body.append("{\nlong start = System.currentTimeMillis();\n");
if (!"void".equals(type)) {
body.append(type + " result = ");
}
body.append(nname + "($);\n");
// finish body text generation with call to print the timing
// information, and return saved value (if not void)
body.append("System.out.println(\"Call to method " + mname +
" took \" +\n (System.currentTimeMillis()-start) + " +
"\" ms.\");\n");
if (!"void".equals(type)) {
body.append("return result;\n");
}
body.append("}");
// replace the body of the interceptor method with generated
// code block and add it to class
mnew.setBody(body.toString());
clas.addMethod(mnew);
// print the generated code block just to show what was done
System.out.println("Interceptor method body:");
System.out.println(body.toString());
}
}
Java编程的动态性， 第4部分: 用Javassist进行类转换(4)时间:2011-04-09 IBM Dennis M. Sosnoski构造 |
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