Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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.apache.hadoop.hdfs.tools.offlineImageViewer; import static io.netty.handler.codec.http.HttpHeaderNames.CONNECTION; import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_LENGTH; import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_TYPE; import static io.netty.handler.codec.http.HttpHeaderValues.CLOSE; import static io.netty.handler.codec.http.HttpResponseStatus.BAD_REQUEST; import static io.netty.handler.codec.http.HttpResponseStatus.FORBIDDEN; import static io.netty.handler.codec.http.HttpResponseStatus.INTERNAL_SERVER_ERROR; import static io.netty.handler.codec.http.HttpResponseStatus.METHOD_NOT_ALLOWED; import static io.netty.handler.codec.http.HttpResponseStatus.NOT_FOUND; import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1; import static org.apache.hadoop.hdfs.server.datanode.web.webhdfs.WebHdfsHandler.APPLICATION_JSON_UTF8; import static org.apache.hadoop.hdfs.server.datanode.web.webhdfs.WebHdfsHandler.WEBHDFS_PREFIX; import static org.apache.hadoop.hdfs.server.datanode.web.webhdfs.WebHdfsHandler.WEBHDFS_PREFIX_LENGTH; import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.ChannelFutureListener; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.SimpleChannelInboundHandler; import io.netty.channel.group.ChannelGroup; import io.netty.handler.codec.http.DefaultFullHttpResponse; import io.netty.handler.codec.http.DefaultHttpResponse; import io.netty.handler.codec.http.HttpMethod; import io.netty.handler.codec.http.HttpRequest; import io.netty.handler.codec.http.HttpResponseStatus; import io.netty.handler.codec.http.QueryStringDecoder; import java.io.FileNotFoundException; import java.io.IOException; import java.util.List; import java.util.Map; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.hdfs.web.JsonUtil; import org.apache.hadoop.util.StringUtils; import com.google.common.base.Charsets; /** * Implement the read-only WebHDFS API for fsimage. */ class FSImageHandler extends SimpleChannelInboundHandler<HttpRequest> { public static final Log LOG = LogFactory.getLog(FSImageHandler.class); private final FSImageLoader image; private final ChannelGroup activeChannels; @Override public void channelActive(ChannelHandlerContext ctx) throws Exception { activeChannels.add(ctx.channel()); } FSImageHandler(FSImageLoader image, ChannelGroup activeChannels) throws IOException { this.image = image; this.activeChannels = activeChannels; } @Override public void channelRead0(ChannelHandlerContext ctx, HttpRequest request) throws Exception { if (request.method() != HttpMethod.GET) { DefaultHttpResponse resp = new DefaultHttpResponse(HTTP_1_1, METHOD_NOT_ALLOWED); resp.headers().set(CONNECTION, CLOSE); ctx.write(resp).addListener(ChannelFutureListener.CLOSE); return; } QueryStringDecoder decoder = new QueryStringDecoder(request.uri()); final String op = getOp(decoder); final String content; String path = getPath(decoder); switch (op) { case "GETFILESTATUS": content = image.getFileStatus(path); break; case "LISTSTATUS": content = image.listStatus(path); break; case "GETACLSTATUS": content = image.getAclStatus(path); break; case "GETXATTRS": List<String> names = getXattrNames(decoder); String encoder = getEncoder(decoder); content = image.getXAttrs(path, names, encoder); break; case "LISTXATTRS": content = image.listXAttrs(path); break; default: throw new IllegalArgumentException("Invalid value for webhdfs parameter" + " \"op\""); } LOG.info("op=" + op + " target=" + path); DefaultFullHttpResponse resp = new DefaultFullHttpResponse(HTTP_1_1, HttpResponseStatus.OK, Unpooled.wrappedBuffer(content.getBytes(Charsets.UTF_8))); resp.headers().set(CONTENT_TYPE, APPLICATION_JSON_UTF8); resp.headers().set(CONTENT_LENGTH, resp.content().readableBytes()); resp.headers().set(CONNECTION, CLOSE); ctx.write(resp).addListener(ChannelFutureListener.CLOSE); } @Override public void channelReadComplete(ChannelHandlerContext ctx) throws Exception { ctx.flush(); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { Exception e = cause instanceof Exception ? (Exception) cause : new Exception(cause); final String output = JsonUtil.toJsonString(e); ByteBuf content = Unpooled.wrappedBuffer(output.getBytes(Charsets.UTF_8)); final DefaultFullHttpResponse resp = new DefaultFullHttpResponse(HTTP_1_1, INTERNAL_SERVER_ERROR, content); resp.headers().set(CONTENT_TYPE, APPLICATION_JSON_UTF8); if (e instanceof IllegalArgumentException) { resp.setStatus(BAD_REQUEST); } else if (e instanceof FileNotFoundException) { resp.setStatus(NOT_FOUND); } else if (e instanceof IOException) { resp.setStatus(FORBIDDEN); } resp.headers().set(CONTENT_LENGTH, resp.content().readableBytes()); resp.headers().set(CONNECTION, CLOSE); ctx.write(resp).addListener(ChannelFutureListener.CLOSE); } private static String getOp(QueryStringDecoder decoder) { Map<String, List<String>> parameters = decoder.parameters(); return parameters.containsKey("op") ? StringUtils.toUpperCase(parameters.get("op").get(0)) : null; } private static List<String> getXattrNames(QueryStringDecoder decoder) { Map<String, List<String>> parameters = decoder.parameters(); return parameters.get("xattr.name"); } private static String getEncoder(QueryStringDecoder decoder) { Map<String, List<String>> parameters = decoder.parameters(); return parameters.containsKey("encoding") ? parameters.get("encoding").get(0) : null; } private static String getPath(QueryStringDecoder decoder) throws FileNotFoundException { String path = decoder.path(); if (path.startsWith(WEBHDFS_PREFIX)) { return path.substring(WEBHDFS_PREFIX_LENGTH); } else { throw new FileNotFoundException("Path: " + path + " should " + "start with " + WEBHDFS_PREFIX); } } }