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Tomcat example source code file (Param.java)

This example Tomcat source code file (Param.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Tomcat tags/keywords

jsptagexcption, jsptagexcption, param, string, string, tagplugin, tagplugin, tagplugincontext, tagplugincontext

The Tomcat Param.java source code

/*
 * 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.jasper.tagplugins.jstl.core;

import org.apache.jasper.compiler.tagplugin.TagPlugin;
import org.apache.jasper.compiler.tagplugin.TagPluginContext;

public class Param implements TagPlugin {
    
    public void doTag(TagPluginContext ctxt) {
        
        //don't support the body content
        
        //define names of all the temp variables
        String nameName = ctxt.getTemporaryVariableName();
        String valueName = ctxt.getTemporaryVariableName();
        String urlName = ctxt.getTemporaryVariableName();
        String encName = ctxt.getTemporaryVariableName();
        String index = ctxt.getTemporaryVariableName();
        
        //if the param tag has no parents, throw a exception
        TagPluginContext parent = ctxt.getParentContext();
        if(parent == null){
            ctxt.generateJavaSource(" throw new JspTagExcption" +
            "(\"<param> outside <import> or <urlEncode>\");");
            return;
        }
        
        //get the url string before adding this param
        ctxt.generateJavaSource("String " + urlName + " = " +
        "(String)pageContext.getAttribute(\"url_without_param\");");
        
        //get the value of "name"
        ctxt.generateJavaSource("String " + nameName + " = ");
        ctxt.generateAttribute("name");
        ctxt.generateJavaSource(";");
        
        //if the "name" is null then do nothing.
        //else add such string "name=value" to the url.
        //and the url should be encoded
        ctxt.generateJavaSource("if(" + nameName + " != null && !" + nameName + ".equals(\"\")){");
        ctxt.generateJavaSource("    String " + valueName + " = ");
        ctxt.generateAttribute("value");
        ctxt.generateJavaSource(";");
        ctxt.generateJavaSource("    if(" + valueName + " == null) " + valueName + " = \"\";");
        ctxt.generateJavaSource("    String " + encName + " = pageContext.getResponse().getCharacterEncoding();");
        ctxt.generateJavaSource("    " + nameName + " = java.net.URLEncoder.encode(" + nameName + ", " + encName + ");");
        ctxt.generateJavaSource("    " + valueName + " = java.net.URLEncoder.encode(" + valueName + ", " + encName + ");");
        ctxt.generateJavaSource("    int " + index + ";");
        ctxt.generateJavaSource("    " + index + " = " + urlName + ".indexOf(\'?\');");
        //if the current param is the first one, add a "?" ahead of it
        //else add a "&" ahead of it
        ctxt.generateJavaSource("    if(" + index + " == -1){");
        ctxt.generateJavaSource("        " + urlName + " = " + urlName + " + \"?\" + " + nameName + " + \"=\" + " + valueName + ";");
        ctxt.generateJavaSource("    }else{");
        ctxt.generateJavaSource("        " + urlName + " = " + urlName + " + \"&\" + " + nameName + " + \"=\" + " + valueName + ";");
        ctxt.generateJavaSource("    }");
        ctxt.generateJavaSource("    pageContext.setAttribute(\"url_without_param\"," + urlName + ");");
        ctxt.generateJavaSource("}");	
    }
}

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