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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.ActionInvocation;
import com.opensymphony.xwork2.util.LocalizedTextUtil;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;

import java.util.Locale;
import java.util.Map;

/**
 * 
 *
 * An interceptor that handles setting the locale specified in a session as the locale for the current action request.
 * In addition, this interceptor will look for a specific HTTP request parameter and set the locale to whatever value is
 * provided. This means that this interceptor can be used to allow for your application to dynamically change the locale
 * for the user's session or, alternatively, only for the current request (since XWork 2.1.3).
 * This is very useful for applications that require multi-lingual support and want the user to
 * be able to set his or her language preference at any point. The locale parameter is removed during the execution of
 * this interceptor, ensuring that properties aren't set on an action (such as request_locale) that have no typical
 * corresponding setter in your action.
 *
 * For example, using the default parameter name, a request to foo.action?request_locale=en_US, then the
 * locale for US English is saved in the user's session and will be used for all future requests.
 *
 * 
 *
 * 
 Interceptor parameters:
 *
 * 
 *
 * 

 *
 * parameterName (optional) - the name of the HTTP request parameter that dictates the locale to switch to and save
 * in the session. By default this is request_locale
 *
 * requestOnlyParameterName (optional) - the name of the HTTP request parameter that dictates the locale to switch to
 * for the current request only, without saving it in the session. By default this is request_only_locale
 *
 * attributeName (optional) - the name of the session key to store the selected locale. By default this is
 * WW_TRANS_I18N_LOCALE
 *
 * 
 *
 * 
 *
 *  Extending the interceptor:
 *
 * 

 *
 * 
 *
 * There are no known extensions points for this interceptor.
 *
 * 
 *
 * 
 Example code:
 *
 * 
 * 
 * <action name="someAction" class="com.examples.SomeAction">
 *     <interceptor-ref name="i18n"/>
 *     <interceptor-ref name="basicStack"/>
 *     <result name="success">good_result.ftl</result>
 * </action>
 * 
 * 
 *
 * @author Aleksei Gopachenko
 */
public class I18nInterceptor extends AbstractInterceptor {
    protected static final Logger LOG = LoggerFactory.getLogger(I18nInterceptor.class);

    public static final String DEFAULT_SESSION_ATTRIBUTE = "WW_TRANS_I18N_LOCALE";
    public static final String DEFAULT_PARAMETER = "request_locale";
    public static final String DEFAULT_REQUESTONLY_PARAMETER = "request_only_locale";

    protected String parameterName = DEFAULT_PARAMETER;
    protected String requestOnlyParameterName = DEFAULT_REQUESTONLY_PARAMETER;
    protected String attributeName = DEFAULT_SESSION_ATTRIBUTE;

    public I18nInterceptor() {
        if (LOG.isDebugEnabled()) {
            LOG.debug("new I18nInterceptor()");
        }
    }

    public void setParameterName(String parameterName) {
        this.parameterName = parameterName;
    }

    public void setRequestOnlyParameterName( String requestOnlyParameterName ) {
        this.requestOnlyParameterName = requestOnlyParameterName;
    }

    public void setAttributeName(String attributeName) {
        this.attributeName = attributeName;
    }

    @Override
    public String intercept(ActionInvocation invocation) throws Exception {
        if (LOG.isDebugEnabled()) {
            LOG.debug("intercept '"
                    + invocation.getProxy().getNamespace() + "/"
                    + invocation.getProxy().getActionName() + "' { ");
        }
        //get requested locale
        Map params = invocation.getInvocationContext().getParameters();

        boolean storeInSession = true;
        Object requested_locale = findLocaleParameter(params, parameterName);
        if (requested_locale == null) {
        	requested_locale = findLocaleParameter(params, requestOnlyParameterName);
            if (requested_locale != null) {
            	storeInSession = false;
            }
        }

        //save it in session
        Map session = invocation.getInvocationContext().getSession();

        Locale locale = null;
        if (requested_locale != null) {
            locale = (requested_locale instanceof Locale) ?
                    (Locale) requested_locale : LocalizedTextUtil.localeFromString(requested_locale.toString(), null);
            if (locale != null && LOG.isDebugEnabled()) {
                LOG.debug("applied request locale=" + locale);
            }
        }
        if (session != null) {
            synchronized (session) {
                if (locale == null) {
                    // check session for saved locale
                    Object sessionLocale = session.get(attributeName);
                    if (sessionLocale != null && sessionLocale instanceof Locale) {
                        locale = (Locale) sessionLocale;
                        if (LOG.isDebugEnabled()) {
                            LOG.debug("applied session locale=" + locale);
                        }
                    } else {
                        // no overriding locale definition found, stay with current invokation (=browser) locale
                        locale = invocation.getInvocationContext().getLocale();
                        if (locale != null && LOG.isDebugEnabled()) {
                            LOG.debug("applied invocation context locale=" + locale);
                        }
                    }
                }
                if (storeInSession) {
                    session.put(attributeName, locale);
                }
            }
        }
        saveLocale(invocation, locale);

        if (LOG.isDebugEnabled()) {
            LOG.debug("before Locale=" + invocation.getStack().findValue("locale"));
        }

        final String result = invocation.invoke();
        if (LOG.isDebugEnabled()) {
            LOG.debug("after Locale=" + invocation.getStack().findValue("locale"));
        }

        if (LOG.isDebugEnabled()) {
            LOG.debug("intercept } ");
        }

        return result;
    }

    private Object findLocaleParameter( Map params, String parameterName ) {
        Object requested_locale = params.remove(parameterName);
        if (requested_locale != null && requested_locale.getClass().isArray()
                && ((Object[]) requested_locale).length == 1) {
            requested_locale = ((Object[]) requested_locale)[0];

            if (LOG.isDebugEnabled()) {
                LOG.debug("requested_locale=" + requested_locale);
            }
        }
        return requested_locale;
    }

    /**
     * Save the given locale to the ActionInvocation.
     *
     * @param invocation The ActionInvocation.
     * @param locale The locale to save.
     */
    protected void saveLocale(ActionInvocation invocation, Locale locale) {
        invocation.getInvocationContext().setLocale(locale);
    }

}