org.maodian.flyingcat.netty.handler.XMLFragmentDecoder.java Source code

Introduction

Here is the source code for org.maodian.flyingcat.netty.handler.XMLFragmentDecoder.java

Source

/*
 * Copyright 2013 - 2013 Cole Wen
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.maodian.flyingcat.netty.handler;

import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageDecoder;

import java.lang.invoke.MethodHandles;

import org.apache.commons.lang3.StringUtils;
import org.maodian.flyingcat.xmpp.state.StreamError;
import org.maodian.flyingcat.xmpp.state.XmppException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @author Cole Wen
 *
 */
public class XMLFragmentDecoder extends MessageToMessageDecoder<String> {
    private static final Logger logger = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
    private static final String[] INVALID_ELEMENT_HEADS = { "<!", //DOCTYPE and ENTITY reference
    };
    private static final String[] INVALID_ELEMENT_TAILS = { "-->", // comments 
            "]]>", // CDATA
    };
    private static final String PROCESS_INSTRUCTION_TAIL = "?>"; // processing instructions"

    private int depth = 0;
    private StringBuilder xml;
    //private boolean acceptXMLDeclaration = true;

    /* (non-Javadoc)
     * @see io.netty.handler.codec.MessageToMessageDecoder#decode(io.netty.channel.ChannelHandlerContext, java.lang.Object)
     */
    @Override
    protected Object decode(ChannelHandlerContext ctx, String msg) throws Exception {
        if (StringUtils.endsWithAny(msg, INVALID_ELEMENT_TAILS)) {
            throw new XmppException(StreamError.RESTRICTED_XML).set("xml", msg);
        }

        if (StringUtils.endsWith(msg, PROCESS_INSTRUCTION_TAIL) && !StringUtils.startsWith(msg, "<?xml ")) {
            throw new XmppException(StreamError.RESTRICTED_XML).set("xml", msg);
        }

        if (StringUtils.startsWithAny(msg, INVALID_ELEMENT_HEADS)) {
            throw new XmppException(StreamError.RESTRICTED_XML).set("xml", msg);
        }

        // always accept xml declaration to improve compability with some client
        if (StringUtils.startsWith(msg, "<?xml ")) {
            return msg;
            /*if (acceptXMLDeclaration) {
              acceptXMLDeclaration = false;
              return msg;
            } else {
              throw new XmppException("XML declaration has been already received before", StreamError.NOT_WELL_FORMED).set("xml", msg);
            }*/
        }

        // deal with stream tag
        if (StringUtils.contains(msg, ":stream")
                && (StringUtils.contains(msg, "<") || StringUtils.contains(msg, "</"))) {
            if (depth != 0) {
                throw new XmppException("Stream Open/Close Tag can only be root element", StreamError.INVALID_XML);
            }
            return msg;
        }

        // deal with empty element at first level
        if (depth == 0 && StringUtils.endsWith(msg, "/>")) {
            return msg;
        }

        if (xml == null) {
            xml = new StringBuilder(msg);
        } else {
            xml.append(msg);
        }

        // deal with nested empty element
        if (StringUtils.endsWith(msg, "/>")) {
            return null;
        }

        if (StringUtils.contains(msg, "</")) {
            depth--;
        } else if (StringUtils.contains(msg, "<")) {
            depth++;
        }

        if (depth == 0) {
            String fragment = xml.toString();
            xml = null;
            return fragment;
        }
        return null;
    }

    /* (non-Javadoc)
     * @see io.netty.channel.ChannelHandlerAdapter#exceptionCaught(io.netty.channel.ChannelHandlerContext, java.lang.Throwable)
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        if (cause instanceof XmppException) {
            XmppException xmppException = (XmppException) cause;
            StringBuilder xml = new StringBuilder(xmppException.getXmppError().toXML()).append("</stream:stream>");
            ctx.write(xml.toString()).addListener(ChannelFutureListener.CLOSE);
            logger.error("Close the XMPP Stream due to error", cause);
        }
        super.exceptionCaught(ctx, cause);
    }
}