parametertag.java

structs源码

/*
 * $Id: ParameterTag.java 471754 2006-11-06 14:55:09Z husted $
 *
 * 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.
 */
package org.apache.struts.taglib.bean;

import org.apache.struts.taglib.TagUtils;
import org.apache.struts.util.MessageResources;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;

/**
 * Define a scripting variable based on the value(s) of the specified
 * parameter received with this request.
 *
 * @version $Rev: 471754 $ $Date: 2004-10-16 12:38:42 -0400 (Sat, 16 Oct 2004)
 *          $
 */
public class ParameterTag extends TagSupport {
    /**
     * The message resources for this package.
     */
    protected static MessageResources messages =
        MessageResources.getMessageResources(
            "org.apache.struts.taglib.bean.LocalStrings");

    // ------------------------------------------------------------- Properties

    /**
     * The name of the scripting variable that will be exposed as a page scope
     * attribute.
     */
    protected String id = null;

    /**
     * Return an array of parameter values if <code>multiple</code> is
     * non-null.
     */
    protected String multiple = null;

    /**
     * The name of the parameter whose value is to be exposed.
     */
    protected String name = null;

    /**
     * The default value to return if no parameter of the specified name is
     * found.
     */
    protected String value = null;

    public String getId() {
        return (this.id);
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getMultiple() {
        return (this.multiple);
    }

    public void setMultiple(String multiple) {
        this.multiple = multiple;
    }

    public String getName() {
        return (this.name);
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getValue() {
        return (this.value);
    }

    public void setValue(String value) {
        this.value = value;
    }

    // --------------------------------------------------------- Public Methods

    /**
     * Retrieve the required property and expose it as a scripting variable.
     *
     * @throws JspException if a JSP exception has occurred
     */
    public int doStartTag() throws JspException {
        // Deal with a single parameter value
        if (multiple == null) {
            String value = pageContext.getRequest().getParameter(name);

            if ((value == null) && (this.value != null)) {
                value = this.value;
            }

            if (value == null) {
                JspException e =
                    new JspException(messages.getMessage("parameter.get", name));

                TagUtils.getInstance().saveException(pageContext, e);
                throw e;
            }

            pageContext.setAttribute(id, value);

            return (SKIP_BODY);
        }

        // Deal with multiple parameter values
        String[] values = pageContext.getRequest().getParameterValues(name);

        if ((values == null) || (values.length == 0)) {
            if (this.value != null) {
                values = new String[] { this.value };
            }
        }

        if ((values == null) || (values.length == 0)) {
            JspException e =
                new JspException(messages.getMessage("parameter.get", name));

            TagUtils.getInstance().saveException(pageContext, e);
            throw e;
        }

        pageContext.setAttribute(id, values);

        return (SKIP_BODY);
    }

    /**
     * Release all allocated resources.
     */
    public void release() {
        super.release();
        id = null;
        multiple = null;
        name = null;
        value = null;
    }
}