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package org.apache.http.impl.client;

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:
 * 
    *
  1. Application parameters: * expected to be the same for all clients used by an application. * These provide "global", that is application-wide, defaults. *
  2. *
  3. Client parameters: * specific to an instance of * {@link org.apache.http.client.HttpClient HttpClient}. * These provide client specific defaults. *
  4. *
  5. Request parameters: * specific to a single request execution. * For overriding client and global defaults. *
  6. *
  7. 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. *
  8. *
* Each stack entry may be {@code null}. 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' */ @Deprecated public class ClientParamsStack extends AbstractHttpParams { /** The application parameter collection, or {@code null}. */ protected final HttpParams applicationParams; /** The client parameter collection, or {@code null}. */ protected final HttpParams clientParams; /** The request parameter collection, or {@code null}. */ protected final HttpParams requestParams; /** The override parameter collection, or {@code null}. */ 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} * @param cparams client parameters, or {@code null} * @param rparams request parameters, or {@code null} * @param oparams override parameters, or {@code null} */ 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}, * 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} * @param cparams client parameters, or {@code null} * @param rparams request parameters, or {@code null} * @param oparams override parameters, or {@code null} */ 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} */ public final HttpParams getApplicationParams() { return applicationParams; } /** * Obtains the client parameters of this stack. * * @return the client parameters, or {@code null} */ public final HttpParams getClientParams() { return clientParams; } /** * Obtains the request parameters of this stack. * * @return the request parameters, or {@code null} */ public final HttpParams getRequestParams() { return requestParams; } /** * Obtains the override parameters of this stack. * * @return the override parameters, or {@code null} */ 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} if it is not set anywhere in this stack */ @Override 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 not 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 */ @Override public HttpParams setParameter(final String name, final Object value) throws UnsupportedOperationException { throw new UnsupportedOperationException ("Setting parameters in a stack is not supported."); } /** * Does not 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 */ @Override public boolean removeParameter(final String name) { throw new UnsupportedOperationException ("Removing parameters in a stack is not supported."); } /** * Does not 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. *

* Derived classes may change this behavior. *

* * @return {@code this} parameter stack */ @Override public HttpParams copy() { return this; } }




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