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Commons Digester example source code file (CallParamRule.java)
This example Commons Digester source code file (CallParamRule.java) is included in the DevDaily.com
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The Commons Digester CallParamRule.java source code
/* $Id: CallParamRule.java 992060 2010-09-02 19:09:47Z simonetripodi $
*
* 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.commons.digester;
import java.util.Stack;
import org.xml.sax.Attributes;
/**
* <p>Rule implementation that saves a parameter for use by a surrounding
* <code>CallMethodRule.
*
* <p>This parameter may be:
* <ul>
* <li>from an attribute of the current element
* See {@link #CallParamRule(int paramIndex, String attributeName)}
* <li>from current the element body
* See {@link #CallParamRule(int paramIndex)}
* <li>from the top object on the stack.
* See {@link #CallParamRule(int paramIndex, boolean fromStack)}
* <li>the current path being processed (separate Rule).
* See {@link PathCallParamRule}
* </ul>
* </p>
*/
public class CallParamRule extends Rule {
// ----------------------------------------------------------- Constructors
/**
* Construct a "call parameter" rule that will save the body text of this
* element as the parameter value.
*
* <p>Note that if the element is empty the an empty string is
* passed to the target method, not null. And if automatic type conversion
* is being applied (ie if the target function takes something other than
* a string as a parameter) then the conversion will fail if the converter
* class does not accept an empty string as valid input.</p>
*
* @param digester The associated Digester
* @param paramIndex The zero-relative parameter number
*
* @deprecated The digester instance is now set in the {@link Digester#addRule} method.
* Use {@link #CallParamRule(int paramIndex)} instead.
*/
@Deprecated
public CallParamRule(Digester digester, int paramIndex) {
this(paramIndex);
}
/**
* Construct a "call parameter" rule that will save the value of the
* specified attribute as the parameter value.
*
* @param digester The associated Digester
* @param paramIndex The zero-relative parameter number
* @param attributeName The name of the attribute to save
*
* @deprecated The digester instance is now set in the {@link Digester#addRule} method.
* Use {@link #CallParamRule(int paramIndex, String attributeName)} instead.
*/
@Deprecated
public CallParamRule(Digester digester, int paramIndex,
String attributeName) {
this(paramIndex, attributeName);
}
/**
* Construct a "call parameter" rule that will save the body text of this
* element as the parameter value.
*
* <p>Note that if the element is empty the an empty string is
* passed to the target method, not null. And if automatic type conversion
* is being applied (ie if the target function takes something other than
* a string as a parameter) then the conversion will fail if the converter
* class does not accept an empty string as valid input.</p>
*
* @param paramIndex The zero-relative parameter number
*/
public CallParamRule(int paramIndex) {
this(paramIndex, null);
}
/**
* Construct a "call parameter" rule that will save the value of the
* specified attribute as the parameter value.
*
* @param paramIndex The zero-relative parameter number
* @param attributeName The name of the attribute to save
*/
public CallParamRule(int paramIndex,
String attributeName) {
this.paramIndex = paramIndex;
this.attributeName = attributeName;
}
/**
* Construct a "call parameter" rule.
*
* @param paramIndex The zero-relative parameter number
* @param fromStack should this parameter be taken from the top of the stack?
*/
public CallParamRule(int paramIndex, boolean fromStack) {
this.paramIndex = paramIndex;
this.fromStack = fromStack;
}
/**
* Constructs a "call parameter" rule which sets a parameter from the stack.
* If the stack contains too few objects, then the parameter will be set to null.
*
* @param paramIndex The zero-relative parameter number
* @param stackIndex the index of the object which will be passed as a parameter.
* The zeroth object is the top of the stack, 1 is the next object down and so on.
*/
public CallParamRule(int paramIndex, int stackIndex) {
this.paramIndex = paramIndex;
this.fromStack = true;
this.stackIndex = stackIndex;
}
// ----------------------------------------------------- Instance Variables
/**
* The attribute from which to save the parameter value
*/
protected String attributeName = null;
/**
* The zero-relative index of the parameter we are saving.
*/
protected int paramIndex = 0;
/**
* Is the parameter to be set from the stack?
*/
protected boolean fromStack = false;
/**
* The position of the object from the top of the stack
*/
protected int stackIndex = 0;
/**
* Stack is used to allow nested body text to be processed.
* Lazy creation.
*/
protected Stack<String> bodyTextStack;
// --------------------------------------------------------- Public Methods
/**
* Process the start of this element.
*
* @param attributes The attribute list for this element
*/
@Override
public void begin(Attributes attributes) throws Exception {
Object param = null;
if (attributeName != null) {
param = attributes.getValue(attributeName);
} else if(fromStack) {
param = digester.peek(stackIndex);
if (digester.log.isDebugEnabled()) {
StringBuffer sb = new StringBuffer("[CallParamRule]{");
sb.append(digester.match);
sb.append("} Save from stack; from stack?").append(fromStack);
sb.append("; object=").append(param);
digester.log.debug(sb.toString());
}
}
// Have to save the param object to the param stack frame here.
// Can't wait until end(). Otherwise, the object will be lost.
// We can't save the object as instance variables, as
// the instance variables will be overwritten
// if this CallParamRule is reused in subsequent nesting.
if(param != null) {
Object parameters[] = (Object[]) digester.peekParams();
parameters[paramIndex] = param;
}
}
/**
* Process the body text of this element.
*
* @param bodyText The body text of this element
*/
@Override
public void body(String bodyText) throws Exception {
if (attributeName == null && !fromStack) {
// We must wait to set the parameter until end
// so that we can make sure that the right set of parameters
// is at the top of the stack
if (bodyTextStack == null) {
bodyTextStack = new Stack<String>();
}
bodyTextStack.push(bodyText.trim());
}
}
/**
* Process any body texts now.
*/
@Override
public void end(String namespace, String name) {
if (bodyTextStack != null && !bodyTextStack.empty()) {
// what we do now is push one parameter onto the top set of parameters
Object parameters[] = (Object[]) digester.peekParams();
parameters[paramIndex] = bodyTextStack.pop();
}
}
/**
* Render a printable version of this Rule.
*/
@Override
public String toString() {
StringBuffer sb = new StringBuffer("CallParamRule[");
sb.append("paramIndex=");
sb.append(paramIndex);
sb.append(", attributeName=");
sb.append(attributeName);
sb.append(", from stack=");
sb.append(fromStack);
sb.append("]");
return (sb.toString());
}
}
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