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Groovy example source code file (AbstractHttpServlet.java)

This example Groovy source code file (AbstractHttpServlet.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 - Groovy tags/keywords

abstracthttpservlet, abstracthttpservlet, file, http, inc_path_info, ioexception, matcher, net, network, request, resourceexception, resourceexception, response, servlet, servletexception, servletexception, string, string, url, web-inf/groovy

The Groovy AbstractHttpServlet.java source code

/*
 * Copyright 2003-2007 the original author or authors.
 *
 * 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 groovy.servlet;

import groovy.util.ResourceConnector;
import groovy.util.ResourceException;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;

/**
 * A base class dealing with common HTTP servlet API housekeeping aspects.
 * <p/>
 * <h4>Resource name mangling (pattern replacement)
 * <p/>
 * <p/>
 * Also implements Groovy's {@link groovy.util.ResourceConnector} in a dynamic
 * manner. It allows you to modify the resource name that is searched for with a
 * <i>replace all operation. See {@link java.util.regex.Pattern} and
 * {@link java.util.regex.Matcher} for details.
 * The servlet init parameter names are:
 * <pre>
 * resource.name.regex = empty - defaults to null
 * resource.name.replacement = empty - defaults to null
 * resource.name.replace.all = true (default) | false means replaceFirst()
 * </pre>
 * Note: If you specify a regex, you have to specify a replacement string too!
 * Otherwise an exception gets raised.
 * <p/>
 * <h4>Logging and bug-hunting options
 * <p/>
 * <p/>
 * This implementation provides a verbosity flag switching log statements.
 * The servlet init parameter name is:
 * <pre>
 * verbose = false(default) | true
 * </pre>
 * <p/>
 * <p/>
 * In order to support class-loading-troubles-debugging with Tomcat 4 or
 * higher, you can log the class loader responsible for loading some classes.
 * See <a href="http://jira.codehaus.org/browse/GROOVY-861">GROOVY-861 for details.
 * The servlet init parameter name is:
 * <pre>
 * log.GROOVY861 = false(default) | true
 * </pre>
 * <p/>
 * <p/>
 * If you experience class-loading-troubles with Tomcat 4 (or higher) or any
 * other servlet container using custom class loader setups, you can fallback
 * to use (slower) reflection in Groovy's MetaClass implementation. Please
 * contact the dev team with your problem! Thanks.
 * The servlet init parameter name is:
 * <pre>
 * reflection = false(default) | true
 * </pre>
 *
 * @author Christian Stein
 * @author Roshan Dawrani (roshandawrani)
 */
public abstract class AbstractHttpServlet extends HttpServlet implements ResourceConnector {

    /**
     * Content type of the HTTP response.
     */
    public static final String CONTENT_TYPE_TEXT_HTML = "text/html";

    /**
     * Servlet API include key name: path_info
     */
    public static final String INC_PATH_INFO = "javax.servlet.include.path_info";

    /* *** Not used, yet. See comments in getScriptUri(HttpServletRequest). ***
     * Servlet API include key name: request_uri
     */
    public static final String INC_REQUEST_URI = "javax.servlet.include.request_uri";

    /**
     * Servlet API include key name: servlet_path
     */
    public static final String INC_SERVLET_PATH = "javax.servlet.include.servlet_path";

    /**
     * Servlet (or the web application) context.
     */
    protected ServletContext servletContext;

    /**
     * Either <code>null or a compiled pattern matcher read from "{@code resource.name.regex}"
     * and used in {@link AbstractHttpServlet#getScriptUri(HttpServletRequest)}.
     */
    protected Matcher resourceNameMatcher;

    /**
     * The replacement used by the resource name matcher.
     */
    protected String resourceNameReplacement;

    /**
     * The replace method to use on the matcher.
     * <pre>
     * true - replaceAll(resourceNameReplacement); (default)
     * false - replaceFirst(resourceNameReplacement);
     * </pre>
     */
    protected boolean resourceNameReplaceAll;

    /**
     * Controls almost all log output.
     */
    protected boolean verbose;

    /**
     * Encoding to use, becomes charset part of contentType.
     */
    protected String encoding = "UTF-8";

    /**
     * Mirrors the static value of the reflection flag in MetaClass.
     * See AbstractHttpServlet#logGROOVY861
     */
    protected boolean reflection;

    /**
     * Debug flag logging the class the class loader of the request.
     */
    private boolean logGROOVY861;

    /**
     * Initializes all fields with default values.
     */
    public AbstractHttpServlet() {
        this.servletContext = null;
        this.resourceNameMatcher = null;
        this.resourceNameReplacement = null;
        this.resourceNameReplaceAll = true;
        this.verbose = false;
        this.reflection = false;
        this.logGROOVY861 = false;
    }

    /**
     * Interface method for ResourceContainer. This is used by the GroovyScriptEngine.
     */
    public URLConnection getResourceConnection(String name) throws ResourceException {
        String basePath = servletContext.getRealPath("/");
        if (name.startsWith(basePath)) name = name.substring(basePath.length());

        name = name.replaceAll("\\\\", "/");

        //remove the leading / as we are trying with a leading / now
        if (name.startsWith("/")) name = name.substring(1);

        /*
        * Try to locate the resource and return an opened connection to it.
        */
        try {
            String tryScriptName = "/" + name;
            URL url = servletContext.getResource(tryScriptName);
            if (url == null) {
                tryScriptName = "/WEB-INF/groovy/" + name;
                url = servletContext.getResource("/WEB-INF/groovy/" + name);
            }
            if (url == null) {
                throw new ResourceException("Resource \"" + name + "\" not found!");
            } else {
                url = new URL("file", "", servletContext.getRealPath(tryScriptName));
            }
            return url.openConnection();
        } catch (IOException e) {
            throw new ResourceException("Problems getting resource named \"" + name + "\"!", e);
        }
    }

    private boolean isFile(URL ret) {
        return ret != null && ret.getProtocol().equals("file");
    }

    /**
     * Returns the include-aware uri of the script or template file.
     *
     * @param request the http request to analyze
     * @return the include-aware uri either parsed from request attributes or
     *         hints provided by the servlet container
     */
    protected String getScriptUri(HttpServletRequest request) {
        /*
         * Log some debug information for http://jira.codehaus.org/browse/GROOVY-861
         */
        if (logGROOVY861) {
            log("Logging request class and its class loader:");
            log(" c = request.getClass() :\"" + request.getClass() + "\"");
            log(" l = c.getClassLoader() :\"" + request.getClass().getClassLoader() + "\"");
            log(" l.getClass()           :\"" + request.getClass().getClassLoader().getClass() + "\"");
            /*
             * Keep logging, if we're verbose. Else turn it off.
             */
            logGROOVY861 = verbose;
        }

        //
        // NOTE: This piece of code is heavily inspired by Apaches Jasper2!
        // 
        // http://cvs.apache.org/viewcvs.cgi/jakarta-tomcat-jasper/jasper2/ \
        //        src/share/org/apache/jasper/servlet/JspServlet.java?view=markup
        //
        // Why doesn't it use request.getRequestURI() or INC_REQUEST_URI?
        //

        String uri = null;
        String info = null;

        //
        // Check to see if the requested script/template source file has been the
        // target of a RequestDispatcher.include().
        //
        uri = (String) request.getAttribute(INC_SERVLET_PATH);
        if (uri != null) {
            //
            // Requested script/template file has been target of 
            // RequestDispatcher.include(). Its path is assembled from the relevant
            // javax.servlet.include.* request attributes and returned!
            //
            info = (String) request.getAttribute(INC_PATH_INFO);
            if (info != null) {
                uri += info;
            }
            return applyResourceNameMatcher(uri);
        }

        //
        // Requested script/template file has not been the target of a 
        // RequestDispatcher.include(). Reconstruct its path from the request's
        // getServletPath() and getPathInfo() results.
        //
        uri = request.getServletPath();
        info = request.getPathInfo();
        if (info != null) {
            uri += info;
        }

        /*
         * TODO : Enable auto ".groovy" extension replacing here!
         * http://cvs.groovy.codehaus.org/viewrep/groovy/groovy/groovy-core/src/main/groovy/servlet/GroovyServlet.java?r=1.10#l259 
         */

        return applyResourceNameMatcher(uri);
    }

    private String applyResourceNameMatcher(final String aUri) {
        /*
         * mangle resource name with the compiled pattern.
         */
        String uri = aUri;
        Matcher matcher = resourceNameMatcher;
        if (matcher != null) {
            matcher.reset(uri);
            String replaced;
            if (resourceNameReplaceAll) {
                replaced = matcher.replaceAll(resourceNameReplacement);
            } else {
                replaced = matcher.replaceFirst(resourceNameReplacement);
            }
            if (!uri.equals(replaced)) {
                if (verbose) {
                    log("Replaced resource name \"" + uri + "\" with \"" + replaced + "\".");
                }
                uri = replaced;
            }
        }
        return uri;
    }

    /**
     * Parses the http request for the real script or template source file.
     *
     * @param request the http request to analyze
     * @return a file object using an absolute file path name
     */
    protected File getScriptUriAsFile(HttpServletRequest request) {
        String uri = getScriptUri(request);
        String real = servletContext.getRealPath(uri);
        return new File(real).getAbsoluteFile();
    }

    /**
     * Overrides the generic init method to set some debug flags.
     *
     * @param config the servlet configuration provided by the container
     * @throws ServletException if init() method defined in super class
     *                          javax.servlet.GenericServlet throws it
     */
    public void init(ServletConfig config) throws ServletException {
        /*
         * Never forget super.init()!
         */
        super.init(config);

        /*
         * Grab the servlet context.
         */
        this.servletContext = config.getServletContext();

        // Get verbosity hint.
        String value = config.getInitParameter("verbose");
        if (value != null) {
            this.verbose = Boolean.valueOf(value);
        }

        // get encoding
        value = config.getInitParameter("encoding");
        if (value != null) {
            this.encoding = value;
        }

        // And now the real init work...
        if (verbose) {
            log("Parsing init parameters...");
        }

        String regex = config.getInitParameter("resource.name.regex");
        if (regex != null) {
            String replacement = config.getInitParameter("resource.name.replacement");
            if (replacement == null) {
                Exception npex = new NullPointerException("resource.name.replacement");
                String message = "Init-param 'resource.name.replacement' not specified!";
                log(message, npex);
                throw new ServletException(message, npex);
            }
            int flags = 0; // TODO : Parse pattern compile flags.
            this.resourceNameMatcher = Pattern.compile(regex, flags).matcher("");
            this.resourceNameReplacement = replacement;
            String all = config.getInitParameter("resource.name.replace.all");
            if (all != null) {
                this.resourceNameReplaceAll = Boolean.valueOf(all);
            }
        }

        value = config.getInitParameter("logGROOVY861");
        if (value != null) {
            this.logGROOVY861 = Boolean.valueOf(value);
            // nothing else to do here
        }

        /*
         * If verbose, log the parameter values.
         */
        if (verbose) {
            log("(Abstract) init done. Listing some parameter name/value pairs:");
            log("verbose = " + verbose); // this *is* verbose! ;)
            log("reflection = " + reflection);
            log("logGROOVY861 = " + logGROOVY861);
            if (resourceNameMatcher != null) {
                log("resource.name.regex = " + resourceNameMatcher.pattern().pattern());
            } else {
                log("resource.name.regex = null");
            }
            log("resource.name.replacement = " + resourceNameReplacement);
        }
    }

    /**
     * Override this method to set your variables to the Groovy binding.
     * <p>
     * All variables bound the binding are passed to the template source text,
     * e.g. the HTML file, when the template is merged.
     * </p>
     * <p>
     * The binding provided by TemplateServlet does already include some default
     * variables. As of this writing, they are (copied from
     * {@link groovy.servlet.ServletBinding}):
     * <ul>
     * <li>"request" : HttpServletRequest 
     * <li>"response" : HttpServletResponse 
     * <li>"context" : ServletContext 
     * <li>"application" : ServletContext 
     * <li>"session" : request.getSession(false) 
     * </ul>
     * </p>
     * <p>
     * And via implicit hard-coded keywords:
     * <ul>
     * <li>"out" : response.getWriter() 
     * <li>"sout" : response.getOutputStream() 
     * <li>"html" : new MarkupBuilder(response.getWriter()) 
     * </ul>
     * </p>
     * <p>
     * The binding also provides convenient methods:
     * <ul>
     * <li>"forward(String path)" : request.getRequestDispatcher(path).forward(request, response);
     * <li>"include(String path)" : request.getRequestDispatcher(path).include(request, response);
     * <li>"redirect(String location)" : response.sendRedirect(location);
     * </ul>
     * </p>
     * <p/>
     * <p>Example binding all servlet context variables:
     * <pre>
     * class MyServlet extends TemplateServlet {
     * <p/>
     *   protected void setVariables(ServletBinding binding) {
     *     // Bind a simple variable
     *     binding.setVariable("answer", new Long(42));
     * <p/>
     *     // Bind all servlet context attributes...
     *     ServletContext context = (ServletContext) binding.getVariable("context");
     *     Enumeration enumeration = context.getAttributeNames();
     *     while (enumeration.hasMoreElements()) {
     *       String name = (String) enumeration.nextElement();
     *       binding.setVariable(name, context.getAttribute(name));
     *     }
     *   }
     * <p/>
     * }
     * <code>
* </p> * * @param binding to be modified */ protected void setVariables(ServletBinding binding) { // empty } }

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