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. * ==================================================================== * * This software consists of voluntary contributions made by many * individuals on behalf of the Apache Software Foundation. For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. * */ package org.apache.http.impl.client; import org.apache.http.annotation.NotThreadSafe; import org.apache.http.params.AbstractHttpParams; import org.apache.http.params.HttpParams; import org.apache.http.util.Args; /** * Represents a stack of parameter collections. * When retrieving a parameter, the stack is searched in a fixed order * and the first match returned. Setting parameters via the stack is * not supported. To minimize overhead, the stack has a fixed size and * does not maintain an internal array. * The supported stack entries, sorted by increasing priority, are: * <ol> * <li>Application parameters: * expected to be the same for all clients used by an application. * These provide "global", that is application-wide, defaults. * </li> * <li>Client parameters: * specific to an instance of * {@link org.apache.http.client.HttpClient HttpClient}. * These provide client specific defaults. * </li> * <li>Request parameters: * specific to a single request execution. * For overriding client and global defaults. * </li> * <li>Override parameters: * specific to an instance of * {@link org.apache.http.client.HttpClient HttpClient}. * These can be used to set parameters that cannot be overridden * on a per-request basis. * </li> * </ol> * Each stack entry may be <code>null</code>. That is preferable over * an empty params collection, since it avoids searching the empty collection * when looking up parameters. * * @since 4.0 * * @deprecated (4.3) use configuration classes provided 'org.apache.http.config' * and 'org.apache.http.client.config' */ @NotThreadSafe @Deprecated public class ClientParamsStack extends AbstractHttpParams { /** The application parameter collection, or <code>null</code>. */ protected final HttpParams applicationParams; /** The client parameter collection, or <code>null</code>. */ protected final HttpParams clientParams; /** The request parameter collection, or <code>null</code>. */ protected final HttpParams requestParams; /** The override parameter collection, or <code>null</code>. */ protected final HttpParams overrideParams; /** * Creates a new parameter stack from elements. * The arguments will be stored as-is, there is no copying to * prevent modification. * * @param aparams application parameters, or <code>null</code> * @param cparams client parameters, or <code>null</code> * @param rparams request parameters, or <code>null</code> * @param oparams override parameters, or <code>null</code> */ public ClientParamsStack(final HttpParams aparams, final HttpParams cparams, final HttpParams rparams, final HttpParams oparams) { applicationParams = aparams; clientParams = cparams; requestParams = rparams; overrideParams = oparams; } /** * Creates a copy of a parameter stack. * The new stack will have the exact same entries as the argument stack. * There is no copying of parameters. * * @param stack the stack to copy */ public ClientParamsStack(final ClientParamsStack stack) { this(stack.getApplicationParams(), stack.getClientParams(), stack.getRequestParams(), stack.getOverrideParams()); } /** * Creates a modified copy of a parameter stack. * The new stack will contain the explicitly passed elements. * For elements where the explicit argument is <code>null</code>, * the corresponding element from the argument stack is used. * There is no copying of parameters. * * @param stack the stack to modify * @param aparams application parameters, or <code>null</code> * @param cparams client parameters, or <code>null</code> * @param rparams request parameters, or <code>null</code> * @param oparams override parameters, or <code>null</code> */ public ClientParamsStack(final ClientParamsStack stack, final HttpParams aparams, final HttpParams cparams, final HttpParams rparams, final HttpParams oparams) { this((aparams != null) ? aparams : stack.getApplicationParams(), (cparams != null) ? cparams : stack.getClientParams(), (rparams != null) ? rparams : stack.getRequestParams(), (oparams != null) ? oparams : stack.getOverrideParams()); } /** * Obtains the application parameters of this stack. * * @return the application parameters, or <code>null</code> */ public final HttpParams getApplicationParams() { return applicationParams; } /** * Obtains the client parameters of this stack. * * @return the client parameters, or <code>null</code> */ public final HttpParams getClientParams() { return clientParams; } /** * Obtains the request parameters of this stack. * * @return the request parameters, or <code>null</code> */ public final HttpParams getRequestParams() { return requestParams; } /** * Obtains the override parameters of this stack. * * @return the override parameters, or <code>null</code> */ public final HttpParams getOverrideParams() { return overrideParams; } /** * Obtains a parameter from this stack. * See class comment for search order. * * @param name the name of the parameter to obtain * * @return the highest-priority value for that parameter, or * <code>null</code> if it is not set anywhere in this stack */ public Object getParameter(final String name) { Args.notNull(name, "Parameter name"); Object result = null; if (overrideParams != null) { result = overrideParams.getParameter(name); } if ((result == null) && (requestParams != null)) { result = requestParams.getParameter(name); } if ((result == null) && (clientParams != null)) { result = clientParams.getParameter(name); } if ((result == null) && (applicationParams != null)) { result = applicationParams.getParameter(name); } return result; } /** * Does <i>not</i> set a parameter. * Parameter stacks are read-only. It is possible, though discouraged, * to access and modify specific stack entries. * Derived classes may change this behavior. * * @param name ignored * @param value ignored * * @return nothing * * @throws UnsupportedOperationException always */ public HttpParams setParameter(final String name, final Object value) throws UnsupportedOperationException { throw new UnsupportedOperationException("Setting parameters in a stack is not supported."); } /** * Does <i>not</i> remove a parameter. * Parameter stacks are read-only. It is possible, though discouraged, * to access and modify specific stack entries. * Derived classes may change this behavior. * * @param name ignored * * @return nothing * * @throws UnsupportedOperationException always */ public boolean removeParameter(final String name) { throw new UnsupportedOperationException("Removing parameters in a stack is not supported."); } /** * Does <i>not</i> copy parameters. * Parameter stacks are lightweight objects, expected to be instantiated * as needed and to be used only in a very specific context. On top of * that, they are read-only. The typical copy operation to prevent * accidental modification of parameters passed by the application to * a framework object is therefore pointless and disabled. * Create a new stack if you really need a copy. * <br/> * Derived classes may change this behavior. * * @return <code>this</code> parameter stack */ public HttpParams copy() { return this; } }