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Utility code for use with GWT and Mvp4g.
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* C E D A R
* S O L U T I O N S "Software done right."
* S O F T W A R E
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* Copyright (c) 2013-2014 Kenneth J. Pronovici.
* All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the Apache License, Version 2.0.
* See LICENSE for more information about the licensing terms.
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* Author : Kenneth J. Pronovici
* Language : Java 6
* Project : Common Java Functionality
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
package com.cedarsolutions.wiring.gwt.rpc;
import com.cedarsolutions.client.gwt.rpc.proxy.XsrfRpcProxy;
import com.google.gwt.core.ext.typeinfo.JClassType;
import com.google.gwt.core.ext.typeinfo.JMethod;
import com.google.gwt.core.ext.typeinfo.JParameter;
import com.google.gwt.core.ext.typeinfo.JType;
import com.google.gwt.core.ext.typeinfo.TypeOracle;
import com.google.gwt.user.client.rpc.impl.RemoteServiceProxy;
import com.google.gwt.user.rebind.SourceWriter;
import com.google.gwt.user.rebind.rpc.ProxyCreator;
import com.google.gwt.user.rebind.rpc.SerializableTypeOracle;
import com.google.gwt.user.server.rpc.NoXsrfProtect;
import com.google.gwt.user.server.rpc.XsrfProtect;
/**
* Create a customized remote service proxy that knows how to make CSRF/XSRF-protected requests.
*
*
* When you request an RPC interface with GWT.create(MyRemoteService.class),
* GWT normally does some magic to implement an asynchronous proxy over your
* remote service interface. Below, we generate customized code that knows how
* to call the CSRF/XSRF token service before making the actual RPC call. That
* way, RPC clients don't need to know anything about the way the service is
* actually invoked — it's all controlled by annotations.
*
*
*
* The customization is conceptually very simple: for every relevant remote procedure
* call, we want to insert a different RPC call that happens first. The first RPC
* call invokes the standard GWT XSRF/CSRF token service and gets a cryptographic
* token that's needed by the real RPC call. Once we have the token, the real RPC
* call is made as usual. The implementation isn't quite that simple, but hopefully
* it won't be too brittle as time goes on.
*
*
* @see GWT RPC XSRF protection
* @author Kenneth J. Pronovici
*/
public class XsrfRpcProxyCreator extends ProxyCreator {
/** Configured type. */
protected JClassType type;
/** Number of methods that have been XSRF protected so far. */
protected int handled;
/** Instantiates a new proxy creator. */
public XsrfRpcProxyCreator(JClassType type) {
super(type);
this.type = type;
this.handled = 0;
}
/** Return our customized proxy supertype. */
@Override
protected Class getProxySupertype() {
return XsrfRpcProxy.class;
}
/** Get the configured type. */
public JClassType getType() {
return this.type;
}
/** Generates the client's asynchronous proxy method and related utility code. */
@Override
protected void generateProxyMethod(SourceWriter w, SerializableTypeOracle serializableTypeOracle,
TypeOracle typeOracle, JMethod syncMethod, JMethod asyncMethod) {
if (!isMethodXsrfProtected(syncMethod)) {
super.generateProxyMethod(w, serializableTypeOracle, typeOracle, syncMethod, asyncMethod);
} else {
String sequence = String.valueOf(++this.handled);
generateInterfaceRpcMethod(w, asyncMethod, sequence);
generateClientRpcMethod(w, serializableTypeOracle, typeOracle, syncMethod, asyncMethod);
generateTokenCallback(w, asyncMethod, sequence);
}
}
/**
* Checks if specified method is XSRF protected at the class or method level.
*
*
* This is roughly equivalent to com.google.gwt.user.server.Util.isMethodXsrfProtected(),
* but it doesn't deal with method return types. No application-level RPC calls should
* return RPC tokens, anyway.
*
*
* @param method Method to check
*
* @return True if the method is protected, false otherwise.
*/
protected static boolean isMethodXsrfProtected(JMethod method) {
if (method.isAnnotationPresent(XsrfProtect.class)) {
// Method is protected if it's annotated with @XsrfProtect
return true;
} else if (method.isAnnotationPresent(NoXsrfProtect.class)) {
// Method is not protected if it's annotated as @NoXsrfProtect
return false;
} else {
// Otherwise, method is protected if its class is annotated with @XsrfProtect
return method.getEnclosingType().isAnnotationPresent(XsrfProtect.class);
}
}
/**
* Create the method that matches the RPC's interface.
*
*
* Given an RPC method "createExchange", we want to create a proxy
* method that looks like this:
*
*
*
* public void createExchange(java.lang.String name, com.google.gwt.user.client.rpc.AsyncCallback callback) {
* AbstractTokenCallback tokenCallback = new _TokenCallback_createExchange(name, callback);
* com.cedarsolutions.client.gwt.rpc.IXsrfTokenRpcAsync xsrfTokenRpc = getXsrfTokenRpc();
* xsrfTokenRpc.generateXsrfToken(tokenCallback);
* }
*
*
*
* The proxy method calls out to the token service before invoking
* the actual RPC in the callback's onSuccess() method.
*
*
*
* The sequence parameter is incorporated into the generated callback
* name so we don't have problems if a single RPC overloads a method name.
*
*/
protected void generateInterfaceRpcMethod(SourceWriter w, JMethod asyncMethod, String sequence) {
String asyncReturnType = asyncMethod.getReturnType().getErasedType().getQualifiedSourceName();
String asyncMethodName = asyncMethod.getName();
JParameter[] asyncParams = asyncMethod.getParameters();
String callbackClassName = "_TokenCallback_" + asyncMethodName + "_" + sequence;
w.println();
w.print("public ");
w.print(asyncReturnType);
w.print(" ");
w.print(asyncMethodName + "(");
writeMethodParameters(w, asyncParams);
w.println(") {");
w.indent();
w.print("AbstractTokenCallback tokenCallback = new ");
w.print(callbackClassName);
w.print("(");
writeMethodArguments(w, asyncParams);
w.println(");");
w.println("com.cedarsolutions.client.gwt.rpc.IXsrfTokenRpcAsync xsrfTokenRpc = getXsrfTokenRpc();");
w.println("xsrfTokenRpc.generateXsrfToken(tokenCallback);");
w.outdent();
w.println("}");
}
/**
* Create the method that invokes the client service.
*
*
* The goal here is to use exactly the same implementation as the parent
* class (to hopefully future-proof this implementation as Google enhances
* the RPC mechanism), but to change the method name so that it can be
* called as expected from the token callback.
*
*/
protected void generateClientRpcMethod(SourceWriter w, SerializableTypeOracle serializableTypeOracle,
TypeOracle typeOracle, JMethod syncMethod, JMethod asyncMethod) {
JType asyncReturnType = asyncMethod.getReturnType().getErasedType();
String origSignature = "public " + asyncReturnType.getQualifiedSourceName() + " " + asyncMethod.getName();
String newSignature = "public " + asyncReturnType.getQualifiedSourceName() + " _realRpcMethod_" + asyncMethod.getName();
SourceWriter sourceWriter = new StringSourceWriter();
super.generateProxyMethod(sourceWriter, serializableTypeOracle, typeOracle, syncMethod, asyncMethod);
String method = sourceWriter.toString().replaceFirst(origSignature, newSignature);
w.print(method);
}
/**
* Generate the token callback class referenced by the interface method.
*
*
* Given an RPC method "createExchange", we want to create a token callback
* that looks like this:
*
*
*
* public class _TokenCallback_createExchange extends AbstractTokenCallback {
* private java.lang.String name;
* private com.google.gwt.user.client.rpc.AsyncCallback callback;
*
* public _TokenCallback_createExchange(java.lang.String name, com.google.gwt.user.client.rpc.AsyncCallback callback) {
* super(callback);
* this.name = name;
* this.callback = callback;
* }
*
* @Override
* public void invokeRpcMethod() {
* _realRpcMethod_createExchange(name, callback);
* }
* }
*
*
*
* The sequence parameter is incorporated into the generated callback
* name so we don't have problems if a single RPC overloads a method name.
*
*/
protected void generateTokenCallback(SourceWriter w, JMethod asyncMethod, String sequence) {
String asyncMethodName = asyncMethod.getName();
JParameter[] asyncParams = asyncMethod.getParameters();
JParameter callbackParam = asyncParams[asyncParams.length - 1]; // callback is assumed to be the last parameter
String realMethodName = "_realRpcMethod_" + asyncMethodName;
String callbackClassName = "_TokenCallback_" + asyncMethodName + "_" + sequence;
w.println();
w.print("public class ");
w.print(callbackClassName);
w.println(" extends AbstractTokenCallback {");
w.indent();
writePrivateVariables(w, asyncParams);
w.println();
w.print("public ");
w.print(callbackClassName);
w.print("(");
writeMethodParameters(w, asyncParams);
w.println(") {");
w.indent();
w.print("super(");
w.print(callbackParam.getName());
w.println(");");
writeVariableAssignments(w, asyncParams);
w.outdent();
w.println("}");
w.println();
w.println("@Override");
w.println("public void invokeRpcMethod() {");
w.indent();
w.print(realMethodName);
w.print("(");
writeMethodArguments(w, asyncParams);
w.println(");");
w.outdent();
w.println("}");
w.outdent();
w.println("}");
}
/** Write a list of parameters as if they are in a method declaration. */
protected void writeMethodParameters(SourceWriter w, JParameter[] params) {
boolean needsComma = false;
for (JParameter param : params) {
if (needsComma) {
w.print(", ");
} else {
needsComma = true;
}
w.print(param.getType().getErasedType().getQualifiedSourceName());
w.print(" ");
w.print(param.getName());
}
}
/** Write a list of parameters as if they are being passed into a method call. */
protected void writeMethodArguments(SourceWriter w, JParameter[] params) {
boolean needsComma = false;
for (JParameter param : params) {
if (needsComma) {
w.print(", ");
} else {
needsComma = true;
}
w.print(param.getName());
}
}
/** Write a list of parameters as if they are private variables in a class. */
protected void writePrivateVariables(SourceWriter w, JParameter[] params) {
for (JParameter param : params) {
w.print("private ");
w.print(param.getType().getErasedType().getQualifiedSourceName());
w.print(" ");
w.print(param.getName());
w.println(";");
}
}
/** Write a list of parameters as if they are variable assignments. */
protected void writeVariableAssignments(SourceWriter w, JParameter[] params) {
for (JParameter param : params) {
w.print("this.");
w.print(param.getName());
w.print(" = ");
w.print(param.getName());
w.println(";");
}
}
}
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