native的实现?

Question

通过调试,
我struts的action的方法里调用
request.getParameter方法,应该是调用的servlet api 中的
org.apache.catalina.connector.RequestFacade 类的重载的getParameter方法,
public String getParameter(String name) {

    if (request == null) {
        throw new IllegalStateException(
                        sm.getString("requestFacade.nullRequest"));
    }

    if (Globals.IS_SECURITY_ENABLED){
        return (String)AccessController.doPrivileged(
            new GetParameterPrivilegedAction(name));
    } else {
        return request.getParameter(name);
    }
}

然后,上面调用的
return (String)AccessController.doPrivileged(
new GetParameterPrivilegedAction(name));
可我发现doPriviledged是native的,我就不知道tomcat目录下哪个文件里实现的native方法的了....

public static native T doPrivileged(PrivilegedAction action);

Answer 1

这个是Java标准库中的类的native实现，跟Tomcat没关系。如果你用的是Sun的JVM的话，源码是在j2se\src\share\native\java\security\AccessController.c
[code="c"]/*

• Class: java_security_AccessController
• Method: doPrivileged

• Signature: (Ljava/security/PrivilegedAction;)Ljava/lang/Object;
  */
  JNIEXPORT jobject JNICALL Java_java_security_AccessController_doPrivileged__Ljava_security_PrivilegedAction_2
  (JNIEnv *env, jclass cls, jobject action)
  {
  return JVM_DoPrivileged(env, cls, action, NULL, JNI_FALSE);
  }[/code]
  hotspot\src\share\vm\prims\jvm.cpp
  [code="c++"]JVM_ENTRY(jobject, JVM_DoPrivileged(JNIEnv *env, jclass cls, jobject action, jobject context, jboolean wrapException))
  JVMWrapper("JVM_DoPrivileged");

  if (action == NULL) {
  THROW_MSG_0(vmSymbols::java_lang_NullPointerException(), "Null action");
  }

  // Stack allocated list of privileged stack elements
  PrivilegedElement pi;

  // Check that action object understands "Object run()"
  Handle object (THREAD, JNIHandles::resolve(action));

  // get run() method
  methodOop m_oop = Klass::cast(object->klass())->uncached_lookup_method(
  vmSymbols::run_method_name(),
  vmSymbols::void_object_signature());
  methodHandle m (THREAD, m_oop);
  if (m.is_null() || !m->is_method() || !methodOop(m())->is_public() || methodOop(m())->is_static()) {
  THROW_MSG_0(vmSymbols::java_lang_InternalError(), "No run method");
  }

  // Compute the frame initiating the do privileged operation and setup the privileged stack
  vframeStream vfst(thread);
  vfst.security_get_caller_frame(1);

  if (!vfst.at_end()) {
  pi.initialize(&vfst, JNIHandles::resolve(context), thread->privileged_stack_top(), CHECK_NULL);
  thread->set_privileged_stack_top(&pi);
  }

  // invoke the Object run() in the action object. We cannot use call_interface here, since the static type
  // is not really known - it is either java.security.PrivilegedAction or java.security.PrivilegedExceptionAction
  Handle pending_exception;
  JavaValue result(T_OBJECT);
  JavaCallArguments args(object);
  JavaCalls::call(&result, m, &args, THREAD);

  // done with action, remove ourselves from the list
  if (!vfst.at_end()) {
  assert(thread->privileged_stack_top() != NULL && thread->privileged_stack_top() == &pi, "wrong top element");
  thread->set_privileged_stack_top(thread->privileged_stack_top()->next());
  }

  if (HAS_PENDING_EXCEPTION) {
  pending_exception = Handle(THREAD, PENDING_EXCEPTION);
  CLEAR_PENDING_EXCEPTION;

  if ( pending_exception->is_a(SystemDictionary::exception_klass()) &&
  !pending_exception->is_a(SystemDictionary::runtime_exception_klass())) {
  // Throw a java.security.PrivilegedActionException(Exception e) exception
  JavaCallArguments args(pending_exception);
  THROW_ARG_0(vmSymbolHandles::java_security_PrivilegedActionException(),
  vmSymbolHandles::exception_void_signature(),
  &args);
  }
  }

  if (pending_exception.not_null()) THROW_OOP_0(pending_exception());
  return JNIHandles::make_local(env, (oop) result.get_jobject());
  JVM_END[/code]
  这些源码可以从Sun的官网获取，http://download.java.net/jdk6/source/ ，也可以下载OpenJDK版，http://download.java.net/openjdk/jdk6/