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XWork is an command-pattern framework that is used to power WebWork as well as other applications. XWork provides an Inversion of Control container, a powerful expression language, data type conversion, validation, and pluggable configuration.

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/*
 * Copyright (c) 2002-2006 by OpenSymphony
 * All rights reserved.
 */

package com.opensymphony.xwork2.interceptor;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.config.entities.ActionConfig;
import com.opensymphony.xwork2.util.ValueStack;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.util.Iterator;
import java.util.Map;


/**
 * 
 *
 * The aim of this Interceptor is to alias a named parameter to a different named parameter. By acting as the glue
 * between actions sharing similiar parameters (but with different names), it can help greatly with action chaining.
 *
 *   Action's alias expressions should be in the form of  #{ "name1" : "alias1", "name2" : "alias2" }. This means
 * that assuming an action (or something else in the stack) has a value for the expression named name1 and the
 * action this interceptor is applied to has a setter named alias1, alias1 will be set with the value from
 * name1.
 *
 * 
 *
 * 
 Interceptor parameters:
 *
 * 
 *
 * 

 *
 * aliasesKey (optional) - the name of the action parameter to look for the alias map (by default this is
 * aliases).
 *
 * 
 *
 * 
 *
 *  Extending the interceptor:
 *
 * 

 *
 * 
 *
 * This interceptor does not have any known extension points.
 *
 * 
 *
 * 
 Example code:
 *
 * 
 * 
 * <action name="someAction" class="com.examples.SomeAction">
 *     <!-- The value for the foo parameter will be applied as if it were named bar -->
 *     <param name="aliases">#{ 'foo' : 'bar' }</param>
 *
 *     <interceptor-ref name="alias"/>
 *     <interceptor-ref name="basicStack"/>
 *     <result name="success">good_result.ftl</result>
 * </action>
 * 
 * 
 *
 * @author Matthew Payne
 */
public class AliasInterceptor extends AbstractInterceptor {
    private static final Log log = LogFactory.getLog(AliasInterceptor.class);
    private static final String DEFAULT_ALIAS_KEY = "aliases";

    protected String aliasesKey = DEFAULT_ALIAS_KEY;

    public void setAliasesKey(String aliasesKey) {
        this.aliasesKey = aliasesKey;
    }

    public String intercept(ActionInvocation invocation) throws Exception {

        ActionConfig config = invocation.getProxy().getConfig();
        ActionContext ac = invocation.getInvocationContext();

        // get the action's parameters
        final Map parameters = config.getParams();

        if (parameters.containsKey(aliasesKey)) {

            String aliasExpression = (String) parameters.get(aliasesKey);
            ValueStack stack = ac.getValueStack();
            Object obj = stack.findValue(aliasExpression);

            if (obj != null && obj instanceof Map) {
                // override
                Map aliases = (Map) obj;
                Iterator itr = aliases.entrySet().iterator();
                while (itr.hasNext()) {
                    Map.Entry entry = (Map.Entry) itr.next();
                    String name = entry.getKey().toString();
                    String alias = (String) entry.getValue();
                    Object value = stack.findValue(name);
                    if (null == value) {
                        // workaround
                        Map contextParameters = (Map) stack.getContext().get("parameters");
                        
                        if (null != contextParameters) {
                            value = contextParameters.get(name);
                        }
                    }
                    if (null != value) {
                        stack.setValue(alias, value);
                    }
                }
            } else {
                log.debug("invalid alias expression:" + aliasesKey);
            }
        }
        
        return invocation.invoke();
    }
}