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Tomcat example source code file (Util.java)

This example Tomcat source code file (Util.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

bytearrayoutputstream, highest_special, http, illegalstateexception, io, printwriter, request, response, servlet, servletoutputstream, servletoutputstream, string, string, stringbuffer, stringbuffer, stringwriter, stringwriter, target, unexpected, util

The Tomcat Util.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;

import org.apache.jasper.Constants;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.util.Locale;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.PageContext;

/**
 * Util contains some often used consts, static methods and embedded class
 * to support the JSTL tag plugin.
 */

public class Util {
    
    public static final String VALID_SCHEME_CHAR = 
        "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789+.-";
    
    public static final String DEFAULT_ENCODING = 
        "ISO-8859-1";
    
    public static final int HIGHEST_SPECIAL = '>';
    
    public static char[][] specialCharactersRepresentation = new char[HIGHEST_SPECIAL + 1][];
    
    static {
        specialCharactersRepresentation['&'] = "&".toCharArray();
        specialCharactersRepresentation['<'] = "<".toCharArray();
        specialCharactersRepresentation['>'] = ">".toCharArray();
        specialCharactersRepresentation['"'] = """.toCharArray();
        specialCharactersRepresentation['\''] = "'".toCharArray();
    }
    
    /**
     * Converts the given string description of a scope to the corresponding
     * PageContext constant.
     *
     * The validity of the given scope has already been checked by the
     * appropriate TLV.
     *
     * @param scope String description of scope
     *
     * @return PageContext constant corresponding to given scope description
     * 
     * taken from org.apache.taglibs.standard.tag.common.core.Util  
     */
    public static int getScope(String scope){
        int ret = PageContext.PAGE_SCOPE;
        
        if("request".equalsIgnoreCase(scope)){
            ret = PageContext.REQUEST_SCOPE;
        }else if("session".equalsIgnoreCase(scope)){
            ret = PageContext.SESSION_SCOPE;
        }else if("application".equalsIgnoreCase(scope)){
            ret = PageContext.APPLICATION_SCOPE;
        }
        
        return ret;
    }
    
    /**
     * Returns <tt>true if our current URL is absolute,
     * <tt>false otherwise.
     * taken from org.apache.taglibs.standard.tag.common.core.ImportSupport
     */
    public static boolean isAbsoluteUrl(String url){
        if(url == null){
            return false;
        }
        
        int colonPos = url.indexOf(":");
        if(colonPos == -1){
            return false;
        }
        
        for(int i=0;i<colonPos;i++){
            if(VALID_SCHEME_CHAR.indexOf(url.charAt(i)) == -1){
                return false;
            }
        }
        
        return true;
    }
    
    /**
     * Get the value associated with a content-type attribute.
     * Syntax defined in RFC 2045, section 5.1.
     * taken from org.apache.taglibs.standard.tag.common.core.Util
     */
    public static String getContentTypeAttribute(String input, String name) {
        int begin;
        int end;
        int index = input.toUpperCase().indexOf(name.toUpperCase());
        if (index == -1) return null;
        index = index + name.length(); // positioned after the attribute name
        index = input.indexOf('=', index); // positioned at the '='
        if (index == -1) return null;
        index += 1; // positioned after the '='
        input = input.substring(index).trim();
        
        if (input.charAt(0) == '"') {
            // attribute value is a quoted string
            begin = 1;
            end = input.indexOf('"', begin);
            if (end == -1) return null;
        } else {
            begin = 0;
            end = input.indexOf(';');
            if (end == -1) end = input.indexOf(' ');
            if (end == -1) end = input.length();
        }
        return input.substring(begin, end).trim();
    }
    
    /**
     * Strips a servlet session ID from <tt>url.  The session ID
     * is encoded as a URL "path parameter" beginning with "jsessionid=".
     * We thus remove anything we find between ";jsessionid=" (inclusive)
     * and either EOS or a subsequent ';' (exclusive).
     * 
     * taken from org.apache.taglibs.standard.tag.common.core.ImportSupport
     */
    public static String stripSession(String url) {
        StringBuffer u = new StringBuffer(url);
        int sessionStart;
        while ((sessionStart = u.toString().indexOf(";" + Constants.SESSION_PARAMETER_NAME + "=")) != -1) {
            int sessionEnd = u.toString().indexOf(";", sessionStart + 1);
            if (sessionEnd == -1)
                sessionEnd = u.toString().indexOf("?", sessionStart + 1);
            if (sessionEnd == -1) 				// still
                sessionEnd = u.length();
            u.delete(sessionStart, sessionEnd);
        }
        return u.toString();
    }
    
    
    /**
     * Performs the following substring replacements
     * (to facilitate output to XML/HTML pages):
     *
     *    & -> &
     *    < -> <
     *    > -> >
     *    " -> "
     *    ' -> '
     *
     * See also OutSupport.writeEscapedXml().
     * 
     * taken from org.apache.taglibs.standard.tag.common.core.Util
     */
    public static String escapeXml(String buffer) {
        int start = 0;
        int length = buffer.length();
        char[] arrayBuffer = buffer.toCharArray();
        StringBuffer escapedBuffer = null;
        
        for (int i = 0; i < length; i++) {
            char c = arrayBuffer[i];
            if (c <= HIGHEST_SPECIAL) {
                char[] escaped = specialCharactersRepresentation[c];
                if (escaped != null) {
                    // create StringBuffer to hold escaped xml string
                    if (start == 0) {
                        escapedBuffer = new StringBuffer(length + 5);
                    }
                    // add unescaped portion
                    if (start < i) {
                        escapedBuffer.append(arrayBuffer,start,i-start);
                    }
                    start = i + 1;
                    // add escaped xml
                    escapedBuffer.append(escaped);
                }
            }
        }
        // no xml escaping was necessary
        if (start == 0) {
            return buffer;
        }
        // add rest of unescaped portion
        if (start < length) {
            escapedBuffer.append(arrayBuffer,start,length-start);
        }
        return escapedBuffer.toString();
    }
    
    /** Utility methods
     * taken from org.apache.taglibs.standard.tag.common.core.UrlSupport
     */
    public static String resolveUrl(
            String url, String context, PageContext pageContext)
    throws JspException {
        // don't touch absolute URLs
        if (isAbsoluteUrl(url))
            return url;
        
        // normalize relative URLs against a context root
        HttpServletRequest request =
            (HttpServletRequest) pageContext.getRequest();
        if (context == null) {
            if (url.startsWith("/"))
                return (request.getContextPath() + url);
            else
                return url;
        } else {
            if (!context.startsWith("/") || !url.startsWith("/")) {
                throw new JspTagException(
                "In URL tags, when the \"context\" attribute is specified, values of both \"context\" and \"url\" must start with \"/\".");
            }
            if (context.equals("/")) {
                // Don't produce string starting with '//', many
                // browsers interpret this as host name, not as
                // path on same host.
                return url;
            } else {
                return (context + url);
            }
        }
    }
    
    /** Wraps responses to allow us to retrieve results as Strings. 
     * mainly taken from org.apache.taglibs.standard.tag.common.core.importSupport 
     */
    public static class ImportResponseWrapper extends HttpServletResponseWrapper{
        
        private StringWriter sw = new StringWriter();
        private ByteArrayOutputStream bos = new ByteArrayOutputStream();
        private ServletOutputStream sos = new ServletOutputStream() {
            public void write(int b) throws IOException {
                bos.write(b);
            }
        };
        private boolean isWriterUsed;
        private boolean isStreamUsed;
        private int status = 200;
        private String charEncoding;
        
        public ImportResponseWrapper(HttpServletResponse arg0) {
            super(arg0);
            // TODO Auto-generated constructor stub
        }
        
        public PrintWriter getWriter() {
            if (isStreamUsed)
                throw new IllegalStateException("Unexpected internal error during <import>: " +
                "Target servlet called getWriter(), then getOutputStream()");
            isWriterUsed = true;
            return new PrintWriter(sw);
        }
        
        public ServletOutputStream getOutputStream() {
            if (isWriterUsed)
                throw new IllegalStateException("Unexpected internal error during <import>: " +
                "Target servlet called getOutputStream(), then getWriter()");
            isStreamUsed = true;
            return sos;
        }
        
        /** Has no effect. */
        public void setContentType(String x) {
            // ignore
        }
        
        /** Has no effect. */
        public void setLocale(Locale x) {
            // ignore
        }
        
        public void setStatus(int status) {
            this.status = status;
        }
        
        public int getStatus() {
            return status;
        }
        
        public String getCharEncoding(){
            return this.charEncoding;
        }
        
        public void setCharEncoding(String ce){
            this.charEncoding = ce;
        }
        
        public String getString() throws UnsupportedEncodingException {
            if (isWriterUsed)
                return sw.toString();
            else if (isStreamUsed) {
                if (this.charEncoding != null && !this.charEncoding.equals(""))
                    return bos.toString(charEncoding);
                else
                    return bos.toString("ISO-8859-1");
            } else
                return "";		// target didn't write anything
        }
    }
    
}

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