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Tomcat example source code file (SSIConditional.java)

This example Tomcat source code file (SSIConditional.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

expressionparsetree, expressionparsetree, io, parseexception, printwriter, printwriter, ssicommand, ssiconditional, ssiconditionalstate, ssimediator, ssistopprocessingexception, ssistopprocessingexception, string, string, text

The Tomcat SSIConditional.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.catalina.ssi;


import java.io.PrintWriter;
import java.text.ParseException;
/**
 * SSI command that handles all conditional directives.
 * 
 * @version $Revision: 531303 $
 * @author Paul Speed
 * @author David Becker
 */
public class SSIConditional implements SSICommand {
    /**
     * @see SSICommand
     */
    public long process(SSIMediator ssiMediator, String commandName,
            String[] paramNames, String[] paramValues, PrintWriter writer)
            throws SSIStopProcessingException {
    	// Assume anything using conditionals was modified by it
    	long lastModified = System.currentTimeMillis();
        // Retrieve the current state information
        SSIConditionalState state = ssiMediator.getConditionalState();
        if ("if".equalsIgnoreCase(commandName)) {
            // Do nothing if we are nested in a false branch
            // except count it
            if (state.processConditionalCommandsOnly) {
                state.nestingCount++;
                return lastModified;
            }
            state.nestingCount = 0;
            // Evaluate the expression
            if (evaluateArguments(paramNames, paramValues, ssiMediator)) {
                // No more branches can be taken for this if block
                state.branchTaken = true;
            } else {
                // Do not process this branch
                state.processConditionalCommandsOnly = true;
                state.branchTaken = false;
            }
        } else if ("elif".equalsIgnoreCase(commandName)) {
            // No need to even execute if we are nested in
            // a false branch
            if (state.nestingCount > 0) return lastModified;
            // If a branch was already taken in this if block
            // then disable output and return
            if (state.branchTaken) {
                state.processConditionalCommandsOnly = true;
                return lastModified;
            }
            // Evaluate the expression
            if (evaluateArguments(paramNames, paramValues, ssiMediator)) {
                // Turn back on output and mark the branch
                state.processConditionalCommandsOnly = false;
                state.branchTaken = true;
            } else {
                // Do not process this branch
                state.processConditionalCommandsOnly = true;
                state.branchTaken = false;
            }
        } else if ("else".equalsIgnoreCase(commandName)) {
            // No need to even execute if we are nested in
            // a false branch
            if (state.nestingCount > 0) return lastModified;
            // If we've already taken another branch then
            // disable output otherwise enable it.
            state.processConditionalCommandsOnly = state.branchTaken;
            // And in any case, it's safe to say a branch
            // has been taken.
            state.branchTaken = true;
        } else if ("endif".equalsIgnoreCase(commandName)) {
            // If we are nested inside a false branch then pop out
            // one level on the nesting count
            if (state.nestingCount > 0) {
                state.nestingCount--;
                return lastModified;
            }
            // Turn output back on
            state.processConditionalCommandsOnly = false;
            // Reset the branch status for any outer if blocks,
            // since clearly we took a branch to have gotten here
            // in the first place.
            state.branchTaken = true;
        } else {
            throw new SSIStopProcessingException();
            //throw new SsiCommandException( "Not a conditional command:" +
            // cmdName );
        }
        return lastModified;
    }


    /**
     * Retrieves the expression from the specified arguments and peforms the
     * necessary evaluation steps.
     */
    private boolean evaluateArguments(String[] names, String[] values,
            SSIMediator ssiMediator) throws SSIStopProcessingException {
        String expr = getExpression(names, values);
        if (expr == null) {
            throw new SSIStopProcessingException();
            //throw new SsiCommandException( "No expression specified." );
        }
        try {
            ExpressionParseTree tree = new ExpressionParseTree(expr,
                    ssiMediator);
            return tree.evaluateTree();
        } catch (ParseException e) {
            //throw new SsiCommandException( "Error parsing expression." );
            throw new SSIStopProcessingException();
        }
    }


    /**
     * Returns the "expr" if the arg name is appropriate, otherwise returns
     * null.
     */
    private String getExpression(String[] paramNames, String[] paramValues) {
        if ("expr".equalsIgnoreCase(paramNames[0])) return paramValues[0];
        return null;
    }
}

Other Tomcat examples (source code examples)

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