Java tutorial
/* Copyright (C) 2011 Comcast Interactive Media, LLC ("Licensor"). 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 com.comcast.cim.rest.client.xhtml; import java.io.IOException; import java.io.UnsupportedEncodingException; import java.net.MalformedURLException; import java.net.URL; import java.util.ArrayList; import java.util.List; import java.util.Map; import org.apache.http.NameValuePair; import org.apache.http.ParseException; import org.apache.http.client.entity.UrlEncodedFormEntity; import org.apache.http.client.methods.HttpGet; import org.apache.http.client.methods.HttpPost; import org.apache.http.client.methods.HttpUriRequest; import org.apache.http.message.BasicNameValuePair; import org.apache.http.util.EntityUtils; import org.jdom.Element; import org.jdom.JDOMException; import org.jdom.xpath.XPath; /** * Used for constructing HTTP requests from hypermedia controls * (links and forms) presented by the server. */ public class RequestBuilder { /** * Constructs a GET request used to follow a link. * @param a The <a> tag in a parsed response body that * is the link we want to follow. * @param context The URL used to retrieve the current * application state (parsed response body), needed so we * can properly interpret relative URLs. * @return {@link HttpUriRequest} * @throws MalformedURLException if the @href attribute of * the tag cannot be combined with the current URL context * to form a valid URL. */ public HttpUriRequest followLink(Element a, URL context) throws MalformedURLException { if (!"a".equalsIgnoreCase(a.getName())) { throw new IllegalArgumentException("can only follow links on <a> tags"); } String href = a.getAttributeValue("href"); if (href == null) { throw new IllegalArgumentException("<a> tag had no @href attribute"); } URL derived = new URL(context, href); return new HttpGet(derived.toString()); } /** * Constructs a GET or POST request used to submit a form. * The HTTP method used is taken from the form's @method * attribute. * @param form The <form> element from the current * application state which is the form that should be * submitted. * @param context The URL used to retrieve the current * application state (parsed response body). This is * used if the form has a relative URL as its @action. * @param args A map of input names to values. For each * <input> or <select> element in the form, * if its @name is a key in {@code args} then the value * in {@code args} is used as the value in the form * submission. If an input's @name is not found in * {@code args} then it will be submitted with whatever * default value is present. * @return A request that can be issued to submit the * form. * @throws JDOMException * @throws ParseException * @throws IOException */ public HttpUriRequest submitForm(Element form, URL context, Map<String, String> args) throws JDOMException, ParseException, IOException { String formMethod = form.getAttributeValue("method"); String formAction = form.getAttributeValue("action"); URL derived = new URL(context, formAction); UrlEncodedFormEntity e = marshalArguments(form, args); if ("GET".equalsIgnoreCase(formMethod)) { String reqUri = null; if (e != null) { String queryParams = EntityUtils.toString(e); reqUri = String.format("%s?%s", derived.toString(), queryParams); } else { reqUri = derived.toString(); } return new HttpGet(reqUri); } else if ("POST".equalsIgnoreCase(formMethod)) { HttpPost post = new HttpPost(derived.toString()); post.setEntity(e); return post; } throw new IllegalArgumentException("form method must be GET or POST"); } protected UrlEncodedFormEntity marshalArguments(Element form, Map<String, String> args) throws JDOMException, UnsupportedEncodingException { List<NameValuePair> keyvals = new ArrayList<NameValuePair>(); marshalInputArguments(form, args, keyvals); marshalSelectArguments(form, args, keyvals); return (keyvals.size() > 0) ? new UrlEncodedFormEntity(keyvals, "UTF-8") : null; } private void marshalInputArguments(Element form, Map<String, String> args, List<NameValuePair> keyvals) throws JDOMException { XPath xpath = XhtmlParser.getXPath("xhtml", "//xhtml:input[@name]"); for (Object o : xpath.selectNodes(form)) { Element input = (Element) o; String inputName = input.getAttributeValue("name"); if (args.containsKey(inputName)) { keyvals.add(new BasicNameValuePair(inputName, args.get(inputName))); } else { String currValue = input.getAttributeValue("value"); if (currValue != null) { keyvals.add(new BasicNameValuePair(inputName, currValue)); } } } } private void marshalSelectArguments(Element form, Map<String, String> args, List<NameValuePair> keyvals) throws JDOMException { XPath xpath = XhtmlParser.getXPath("xhtml", "//xhtml:select"); for (Object o : xpath.selectNodes(form)) { Element select = (Element) o; String selectName = select.getAttributeValue("name"); if (selectName != null && args.containsKey(selectName)) { addAvailableOption(select, args.get(selectName), keyvals); } else if (selectName != null) { addDefaultOption(select, keyvals); } } } private void addAvailableOption(Element select, String chosenValue, List<NameValuePair> keyvals) throws JDOMException { String selectName = select.getAttributeValue("name"); String expr = String.format("//xhtml:option[@value='%s']", chosenValue); XPath optionPath = XhtmlParser.getXPath("xhtml", expr); if (optionPath.selectSingleNode(select) == null) { String msg = String.format("value '%s' was not one of the available options for select '%s'", chosenValue, selectName); throw new IllegalArgumentException(msg); } keyvals.add(new BasicNameValuePair(selectName, chosenValue)); } private void addDefaultOption(Element select, List<NameValuePair> keyvals) throws JDOMException { String selectName = select.getAttributeValue("name"); XPath defaultPath = XhtmlParser.getXPath("xhtml", "//xhtml:option[@selected]"); Element defaultOption = (Element) defaultPath.selectSingleNode(select); if (defaultOption != null) { keyvals.add(new BasicNameValuePair(selectName, defaultOption.getAttributeValue("value", ""))); } } }