今天在使用Digester的时候遇到了一个问题，还没有找到很好的办法解决。
java文件如下：
Digester digester = new Digester();
digester.setValidating(false);
digester.addObjectCreate("catalog", Catalog2.class);
digester.addObjectCreate("catalog/hi/book", Book2.class);
digester.addBeanPropertySetter("catalog/hi/book/author", "author");
digester.addBeanPropertySetter("catalog/hi/book/title", "title");
digester.addSetNext("catalog/book", "addBook");
File input = new File("E:\\MyProjects\\Workspace\\DigesterDemo\\src\\com\\example\\demo2\\example.xml");
Catalog2 c = (Catalog2) digester.parse(input);
System.out.println(c.toString());
xml文件如下：
<?xml version="1.0"?>
<catalog >
<hi>
<book>
<author>Author 1</author>
<title>Title 1</title>
</book>
</hi>
</catalog>
其中，当我加入了hi节点后，输出为null，不加入时，可以处理。即加入了hi节点后，books.size = 0。
不知道这个问题如何才可以搞定，按照struts的源代码可以看出，struts-config/action-mappings/action 这里也同样没有actionMappings这个对象的实例。
后来，终于在自己的代码里面找到了问题， digester.addSetNext("catalog/book", "addBook"); 这里的代码catalog/book中间少了一个hi节点。加上马上就好了。
但解决上面问题的过程中，我还发现了struts下面的ConfigRuleSet对象。代码贴出来。
package org.apache.struts.config;
import org.apache.commons.digester.AbstractObjectCreationFactory;
import org.apache.commons.digester.Digester;
import org.apache.commons.digester.Rule;
import org.apache.commons.digester.RuleSetBase;
import org.apache.struts.util.RequestUtils;
import org.xml.sax.Attributes;
/**
* <p>
* The set of Digester rules required to parse a Struts configuration file (
* <code>struts-config.xml</code>).
* </p>
*
* @author Craig R. McClanahan
* @version $Revision: 1.14 $ $Date: 2002/12/21 04:42:20 $
* @since Struts 1.1
*/
public class ConfigRuleSet extends RuleSetBase {
// --------------------------------------------------------- Public Methods
/**
* <p>
* Add the set of Rule instances defined in this RuleSet to the specified
* <code>Digester</code> instance, associating them with our namespace URI
* (if any). This method should only be called by a Digester instance. These
* rules assume that an instance of
* <code>org.apache.struts.config.ModuleConfig</code> is pushed onto the
* evaluation stack before parsing begins.
* </p>
*
* @param digester
* Digester instance to which the new Rule instances should be
* added.
*/
public void addRuleInstances(Digester digester) {
digester.addObjectCreate("struts-config/data-sources/data-source",
"org.apache.struts.config.DataSourceConfig", "className");
digester.addSetProperties("struts-config/data-sources/data-source");
digester.addSetNext("struts-config/data-sources/data-source",
"addDataSourceConfig",
"org.apache.struts.config.DataSourceConfig");
digester.addRule("struts-config/data-sources/data-source/set-property",
new AddDataSourcePropertyRule());
digester.addRule("struts-config/action-mappings",
new SetActionMappingClassRule());
digester.addFactoryCreate("struts-config/action-mappings/action",
new ActionMappingFactory());
digester.addSetProperties("struts-config/action-mappings/action");
digester.addSetNext("struts-config/action-mappings/action",
"addActionConfig", "org.apache.struts.config.ActionConfig");
digester.addSetProperty(
"struts-config/action-mappings/action/set-property",
"property", "value");
digester.addObjectCreate(
"struts-config/action-mappings/action/exception",
"org.apache.struts.config.ExceptionConfig", "className");
digester
.addSetProperties("struts-config/action-mappings/action/exception");
digester.addSetNext("struts-config/action-mappings/action/exception",
"addExceptionConfig",
"org.apache.struts.config.ExceptionConfig");
digester.addSetProperty(
"struts-config/action-mappings/action/exception/set-property",
"property", "value");
digester.addObjectCreate(
"struts-config/action-mappings/action/forward",
// "org.apache.struts.config.ForwardConfig",
"org.apache.struts.action.ActionForward", "className");
digester
.addSetProperties("struts-config/action-mappings/action/forward");
digester.addSetNext("struts-config/action-mappings/action/forward",
"addForwardConfig", "org.apache.struts.config.ForwardConfig");
digester.addSetProperty(
"struts-config/action-mappings/action/forward/set-property",
"property", "value");
digester.addObjectCreate("struts-config/controller",
"org.apache.struts.config.ControllerConfig", "className");
digester.addSetProperties("struts-config/controller");
digester.addSetNext("struts-config/controller", "setControllerConfig",
"org.apache.struts.config.ControllerConfig");
digester.addSetProperty("struts-config/controller/set-property",
"property", "value");
digester.addObjectCreate("struts-config/form-beans/form-bean",
// "org.apache.struts.config.FormBeanConfig",
"org.apache.struts.action.ActionFormBean", "className");
digester.addSetProperties("struts-config/form-beans/form-bean");
digester.addSetNext("struts-config/form-beans/form-bean",
"addFormBeanConfig", "org.apache.struts.config.FormBeanConfig");
digester.addObjectCreate(
"struts-config/form-beans/form-bean/form-property",
"org.apache.struts.config.FormPropertyConfig", "className");
digester
.addSetProperties("struts-config/form-beans/form-bean/form-property");
digester.addSetNext("struts-config/form-beans/form-bean/form-property",
"addFormPropertyConfig",
"org.apache.struts.config.FormPropertyConfig");
digester
.addSetProperty(
"struts-config/form-beans/form-bean/form-property/set-property",
"property", "value");
digester.addSetProperty(
"struts-config/form-beans/form-bean/set-property", "property",
"value");
digester.addObjectCreate("struts-config/global-exceptions/exception",
"org.apache.struts.config.ExceptionConfig", "className");
digester.addSetProperties("struts-config/global-exceptions/exception");
digester.addSetNext("struts-config/global-exceptions/exception",
"addExceptionConfig",
"org.apache.struts.config.ExceptionConfig");
digester.addSetProperty(
"struts-config/global-exceptions/exception/set-property",
"property", "value");
digester.addObjectCreate("struts-config/global-forwards/forward",
// "org.apache.struts.config.ForwardConfig",
"org.apache.struts.action.ActionForward", "className");
digester.addSetProperties("struts-config/global-forwards/forward");
digester.addSetNext("struts-config/global-forwards/forward",
"addForwardConfig", "org.apache.struts.config.ForwardConfig");
digester.addSetProperty(
"struts-config/global-forwards/forward/set-property",
"property", "value");
digester.addObjectCreate("struts-config/message-resources",
"org.apache.struts.config.MessageResourcesConfig", "className");
digester.addSetProperties("struts-config/message-resources");
digester.addSetNext("struts-config/message-resources",
"addMessageResourcesConfig",
"org.apache.struts.config.MessageResourcesConfig");
digester.addSetProperty("struts-config/message-resources/set-property",
"property", "value");
digester.addObjectCreate("struts-config/plug-in",
"org.apache.struts.config.PlugInConfig");
digester.addSetProperties("struts-config/plug-in");
digester.addSetNext("struts-config/plug-in", "addPlugInConfig",
"org.apache.struts.config.PlugInConfig");
digester.addRule("struts-config/plug-in/set-property",
new PlugInSetPropertyRule());
}
}
/**
* Class that calls <code>addProperty()</code> for the top object on the stack,
* which must be a <code>org.apache.struts.config.DataSourceConfig</code>.
*/
final class AddDataSourcePropertyRule extends Rule {
public AddDataSourcePropertyRule() {
super();
}
public void begin(Attributes attributes) throws Exception {
DataSourceConfig dsc = (DataSourceConfig) digester.peek();
dsc.addProperty(attributes.getValue("property"), attributes
.getValue("value"));
}
}
/**
* Class that records the name and value of a configuration property to be used
* in configuring a <code>PlugIn</code> instance when instantiated.
*/
final class PlugInSetPropertyRule extends Rule {
public PlugInSetPropertyRule() {
super();
}
public void begin(Attributes attributes) throws Exception {
PlugInConfig plugInConfig = (PlugInConfig) digester.peek();
plugInConfig.addProperty(attributes.getValue("property"), attributes
.getValue("value"));
}
}
/**
* Class that sets the name of the class to use when creating action mapping
* instances. The value is set on the object on the top of the stack, which must
* be a <code>org.apache.struts.config.ModuleConfig</code>.
*/
final class SetActionMappingClassRule extends Rule {
public SetActionMappingClassRule() {
super();
}
public void begin(Attributes attributes) throws Exception {
String className = attributes.getValue("type");
if (className != null) {
ModuleConfig mc = (ModuleConfig) digester.peek();
mc.setActionMappingClass(className);
}
}
}
/**
* An object creation factory which creates action mapping instances, taking
* into account the default class name, which may have been specified on the
* parent element and which is made available through the object on the top of
* the stack, which must be a <code>org.apache.struts.config.ModuleConfig</code>
* .
*/
final class ActionMappingFactory extends AbstractObjectCreationFactory {
public Object createObject(Attributes attributes) {
// Identify the name of the class to instantiate
String className = attributes.getValue("className");
if (className == null) {
ModuleConfig mc = (ModuleConfig) digester.peek();
className = mc.getActionMappingClass();
}
// Instantiate the new object and return it
Object actionMapping = null;
try {
actionMapping = RequestUtils.applicationInstance(className);
} catch (Exception e) {
digester.getLogger()
.error("ActionMappingFactory.createObject: ", e);
}
return actionMapping;
}
}