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package org.apache.catalina.ssi;
import java.io.PrintWriter;
import java.text.ParseException;
/**
* SSI command that handles all conditional directives.
*
* @version $Revision: 1.2 $
* @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;
}
}