messagetag.java

来自「jakarta-taglibs」· Java 代码 · 共 266 行

/*
 * Copyright 1999,2004 The Apache Software Foundation.
 *
 * 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 org.apache.taglibs.i18n;

import java.io.IOException;

import java.text.MessageFormat;

import java.util.Arrays;
import java.util.ArrayList;
import java.util.List;
import java.util.ResourceBundle;

import javax.servlet.ServletContext;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.BodyTag;
import javax.servlet.jsp.tagext.BodyTagSupport;

/**
 *  This class implements a body tag that allows you to use a resource bundle
 *  to internationalize content in a web page. The "key" attribute is required,
 *  and is used to look up content in the resource bundle. The "args" attribute
 *  is optional, and if present, provides items to pass to a MessageFormat.
 *
 *  The BundleTag must first be used in order to ensure that the proper bundle
 *  is loaded.
 *  <P>
 *  <H2>Examples</H2>
 *  <PRE>
 *  &lt;i18n:bundle baseName="test"/&gt;
 *  &lt;i18n:getMessage key="test"/&gt;
 *  &lt;i18n:getMessage key="test" args="1,2,3"/&gt;
 *  etc...
 *  </PRE>
 *  <P>
 *
 *  @author <a href="mailto:[e-mail]">Tim Dawson</a>
 *
 */
public class MessageTag extends BodyTagSupport
{
    // instance variables used during processing
    private String               _key = null;
    private String               _value = null;
    private ResourceBundle       _bundle = null;
    private String               _bundleRef = null;
    private Object []		 _args = null;
    private boolean              _debug = false;

    // these are reused for each message tag; luckily tags are thread-safe
    private MessageFormat  _messageFormat = new MessageFormat("");
    private List           _arguments = new ArrayList();

    /**
     *  sets the key to use when looking up the value in the bundle
     */
    public final void setKey(String key)
    {
        _key = key;
    }

    /**
     *  sets the bundle based on a variable defined in the page<br>
     *  if neither bundle or bundleRef are specified, uses the first bundle
     *  defined on the page by the i18n:bundle tag
     */
    public final void setBundleRef(String varName)
    {
        _bundleRef = varName;
    }

    /**
     *  sets the bundle to an actual ResourceBundle object<br>
     *  if neither bundle or bundleRef are specified, uses the bundle most recently
     *  defined on the page by the i18n:bundle tag
     */
    public final void setBundle(ResourceBundle aBundle)
    {
        _bundle = aBundle;
    }

    /**
     *  @return the bundle to use
     */
    private ResourceBundle getBundle() throws JspException
    {
        ResourceBundle bundle = _bundle;
        if ( bundle == null ) {
            if ( _bundleRef != null ) {
                bundle = (ResourceBundle)pageContext.getAttribute(_bundleRef);
                if ( bundle == null ) {
                    throw new JspTagException(
                        "i18n:message tag, could not find bundleRef=" + _bundleRef);
                }
            } else {
                BundleTag bundleTag = (BundleTag)this.findAncestorWithClass(this,BundleTag.class);
                if (bundleTag != null) {
                    return bundleTag.getBundle();
                }
                bundle = ResourceHelper.getBundle(pageContext);
            }
        }
        return bundle;
    }

    /**
     * Turn debugging log messages on or off
     */
    public final void setDebug(boolean value)
    {
        _debug = value;
    }

    /**
     *  adds to the list of arguments used when formatting the message
     */
    protected final void addArg(Object arg)
    {
        _arguments.add(arg);
        if (_debug) {
            ServletContext sc = pageContext.getServletContext();
            sc.log("i18n:message added arg: " + arg.toString());
        }
    }

    /**
     *  allows setting all the arguments at once
     */
    public final void setArgs(Object[] args)
    {
        _args = args;
    }

    /**
     *  clears the argument list so that sub tags can call addArgument
     *  clears out any previous key and value in case key is not provided,
     *  or the value is null
     */
    public final void release()
    {
        super.release();
        if (_arguments != null)
        {
            _arguments.clear();
        }
        _key = null;
        _value = null;
        _bundle = null;
        _bundleRef = null;
        _args = null;
        _debug = false;
        _messageFormat = null;
        _arguments = null;
    }

  /**
   *  locates the bundle and gets the value
   */
  public final int doStartTag() throws JspException
    {
       // Reset value for resource bundle key
       _value = null;

       // ensure we have a key
        if ( _key == null ) {
            throw new JspTagException("i18n:message tag requires a key attribute.");
        }

        ResourceBundle bundle = this.getBundle();
        if ( bundle == null ) {
            throw new JspTagException(
                "i18n:message tag, no bundle available for use.");
        }

        // Reset the arguments
        if (_arguments != null) {
            _arguments.clear();
        }
        if ( _args != null ) {
            _arguments.addAll(Arrays.asList(_args));
        }

        // see if the bundle has a value, if not, we default to the tag contents
        try {
            _value = bundle.getString(_key);
            if (_debug) {
                ServletContext sc = pageContext.getServletContext();
                sc.log("i18n:message tag: template for " + _key + " is: " + _value);
            }
        } catch (java.util.MissingResourceException e) {
            ServletContext sc = pageContext.getServletContext();
            sc.log("i18n:message tag, value not found for key:" + _key);
        }

        return EVAL_BODY_TAG;
    }

    /**
     *  If key is not found, use the body content as a default value.
     */
    public int doAfterBody() throws JspException
    {
        // if the value is null, use the body content
        if ( _value == null ) {
          _value = bodyContent.getString();
        }
        // cleanup
        bodyContent.clearBody();
    	return SKIP_BODY;
    }

    /**
     *  Performs the proper runtime substitution. If an id attribute was
     *  specified, then it is assumed that this tag is merely defining a
     *  string variable; otherwise output is provided.
     */
    public final int doEndTag() throws JspException
    {
        try {
            // perform parameter substitutions
            if ( _value != null && _arguments != null && _arguments.size() > 0) {
                // reformat the value as specified
                _messageFormat.setLocale(getBundle().getLocale());
                _messageFormat.applyPattern(_value);
                _value = _messageFormat.format(_arguments.toArray());
            }

            if ( _value == null) {
                if (_debug) {
                    ServletContext sc = pageContext.getServletContext();
                    sc.log("i18n: message: skipping null value for " + _key);
                }
            } else if (id != null) {
                // define the variable in the page context
                pageContext.setAttribute(id,_value);
            } else {
                // print the value to the JspWriter
                this.pageContext.getOut().print(_value);
            }
        } catch (java.io.IOException e) {
            throw new JspTagException("i18n:message tag IO Error: " + e.getMessage());
        }

        // only process the body once
        return EVAL_PAGE;
    }

}