Java tutorial
/* * Copyright 2015 LinkedIn Corp. * * 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 azkaban.utils; import java.io.IOException; import java.io.UnsupportedEncodingException; import java.net.URI; import java.net.URISyntaxException; import java.util.List; import org.apache.http.HttpEntity; import org.apache.http.HttpMessage; import org.apache.http.HttpResponse; import org.apache.http.NameValuePair; import org.apache.http.ParseException; import org.apache.http.client.HttpResponseException; import org.apache.http.client.methods.HttpDelete; import org.apache.http.client.methods.HttpEntityEnclosingRequestBase; import org.apache.http.client.methods.HttpGet; import org.apache.http.client.methods.HttpPost; import org.apache.http.client.methods.HttpPut; import org.apache.http.client.methods.HttpUriRequest; import org.apache.http.client.utils.URIBuilder; import org.apache.http.entity.ByteArrayEntity; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.log4j.Logger; /** class handles the communication between the application and * a Restful API based web server. * @param T : type of the returning response object. * Note: the idea of this abstract class is to provide a wrapper for the logic around HTTP layer communication so * development work can take this as a black box and focus on processing the result. * With that said the abstract class will be provided as a template, which ideally can support different types * of returning object (Dictionary, xmlDoc , text etc.) * */ public abstract class RestfulApiClient<T> { protected static Logger logger = Logger.getLogger(RestfulApiClient.class); /** Method to transform the response returned by the httpClient into the * type specified. * Note: Method need to handle case such as failed request. * Also method is not supposed to pass the response object out * via the returning value as the response will be closed after the * execution steps out of the method context. * @throws HttpResponseException * @throws IOException * @throws ParseException * **/ protected abstract T parseResponse(HttpResponse response) throws HttpResponseException, IOException; /** function to perform a Get http request. * @param uri the URI of the request. * @param headerEntries extra entries to be added to request header. * @return the response object type of which is specified by user. * @throws IOException */ public T httpGet(URI uri, List<NameValuePair> headerEntries) throws IOException { // shortcut if the passed url is invalid. if (null == uri) { logger.error(" unable to perform httpGet as the passed uri is null"); return null; } HttpGet get = new HttpGet(uri); return this.sendAndReturn((HttpGet) completeRequest(get, headerEntries)); } /** function to perform a Post http request. * @param uri the URI of the request. * @param headerEntries extra entries to be added to request header. * @param postingBody the content to be posted , optional. * @return the response object type of which is specified by user. * @throws UnsupportedEncodingException, IOException */ public T httpPost(URI uri, List<NameValuePair> headerEntries, String postingBody) throws UnsupportedEncodingException, IOException { // shortcut if the passed url is invalid. if (null == uri) { logger.error(" unable to perform httpPost as the passed uri is null."); return null; } HttpPost post = new HttpPost(uri); return this.sendAndReturn(completeRequest(post, headerEntries, postingBody)); } /** function to perform a Delete http request. * @param uri the URI of the request. * @param headerEntries extra entries to be added to request header. * @return the response object type of which is specified by user. * @throws IOException */ public T httpDelete(URI uri, List<NameValuePair> headerEntries) throws IOException { // shortcut if the passed url is invalid. if (null == uri) { logger.error(" unable to perform httpDelete as the passed uri is null."); return null; } HttpDelete delete = new HttpDelete(uri); return this.sendAndReturn((HttpDelete) completeRequest(delete, headerEntries)); } /** function to perform a Put http request. * @param uri the URI of the request. * @param headerEntries extra entries to be added to request header. * @param postingBody the content to be posted , optional. * @return the response object type of which is specified by user. * @throws UnsupportedEncodingException, IOException */ public T httpPut(URI uri, List<NameValuePair> headerEntries, String postingBody) throws UnsupportedEncodingException, IOException { // shortcut if the passed url is invalid. if (null == uri) { logger.error(" unable to perform httpPut as the passed url is null or empty."); return null; } HttpPut put = new HttpPut(uri); return this.sendAndReturn(completeRequest(put, headerEntries, postingBody)); } /** function to dispatch the request and pass back the response. * */ protected T sendAndReturn(HttpUriRequest request) throws IOException { CloseableHttpClient client = HttpClients.createDefault(); try { return this.parseResponse(client.execute(request)); } finally { client.close(); } } /** helper function to build a valid URI. * @param host host name. * @param port host port. * @param path extra path after host. * @param isHttp indicates if whether Http or HTTPS should be used. * @param params extra query parameters. * @return the URI built from the inputs. * @throws IOException * */ public static URI buildUri(String host, int port, String path, boolean isHttp, Pair<String, String>... params) throws IOException { URIBuilder builder = new URIBuilder(); builder.setScheme(isHttp ? "http" : "https").setHost(host).setPort(port); if (null != path && path.length() > 0) { builder.setPath(path); } if (params != null) { for (Pair<String, String> pair : params) { builder.setParameter(pair.getFirst(), pair.getSecond()); } } URI uri = null; try { uri = builder.build(); } catch (URISyntaxException e) { throw new IOException(e); } return uri; } /** helper function to build a valid URI. * @param uri the URI to start with. * @param params extra query parameters to append. * @return the URI built from the inputs. * @throws IOException * */ public static URI BuildUri(URI uri, Pair<String, String>... params) throws IOException { URIBuilder builder = new URIBuilder(uri); if (params != null) { for (Pair<String, String> pair : params) { builder.setParameter(pair.getFirst(), pair.getSecond()); } } URI returningUri = null; try { returningUri = builder.build(); } catch (URISyntaxException e) { throw new IOException(e); } return returningUri; } /** helper function to fill the request with header entries . * */ private static HttpMessage completeRequest(HttpMessage request, List<NameValuePair> headerEntries) { if (null == request) { logger.error("unable to complete request as the passed request object is null"); return request; } // dump all the header entries to the request. if (null != headerEntries && headerEntries.size() > 0) { for (NameValuePair pair : headerEntries) { request.addHeader(pair.getName(), pair.getValue()); } } return request; } /** helper function to fill the request with header entries and posting body . * */ private static HttpEntityEnclosingRequestBase completeRequest(HttpEntityEnclosingRequestBase request, List<NameValuePair> headerEntries, String postingBody) throws UnsupportedEncodingException { if (null != completeRequest(request, headerEntries)) { // dump the post body UTF-8 will be used as the default encoding type. if (null != postingBody && postingBody.length() > 0) { HttpEntity entity = new ByteArrayEntity(postingBody.getBytes("UTF-8")); request.setHeader("Content-Length", Long.toString(entity.getContentLength())); request.setEntity(entity); } } return request; } }