哪位老大能夠解釋下這段程式碼

gelu發表於2004-08-12
package org.ofbiz.core.event;

import java.util.*;
import java.lang.reflect.*;
import javax.servlet.http.*;

import org.ofbiz.core.util.*;

/**
* JavaEventHandler - Static Method Java Event Handler
*
* @author <a href="mailto:jaz@ofbiz.org">Andy Zeneski</a>
* @author <a href="mailto:jonesde@ofbiz.org">David E. Jones</a>
* @version $Revision: 1.17 $
* @since 2.0
*/
public class JavaEventHandler implements EventHandler {

public static final String module = JavaEventHandler.class.getName();

private Map eventClassMap = new HashMap();

/**
* Invoke the web event
* @param eventPath The path or location of this event
* @param eventMethod The method to invoke
* @param request The servlet request object
* @param response The servlet response object
* @return String Result code
* @throws EventHandlerException
*/
public String invoke(String eventPath, String eventMethod, HttpServletRequest request, HttpServletResponse response) throws EventHandlerException {
Class eventClass = (Class) this.eventClassMap.get(eventPath);

if (eventClass == null) {
synchronized (this) {
eventClass = (Class) this.eventClassMap.get(eventPath);
if (eventClass == null) {
try {
ClassLoader loader = Thread.currentThread().getContextClassLoader();
eventClass = loader.loadClass(eventPath);
} catch (ClassNotFoundException e) {
Debug.logError(e, "Error loading class with name: " + eventPath + ", will not be able to run event...");
}
if (eventClass != null) {
eventClassMap.put(eventPath, eventClass);
}
}
}
}
if (Debug.verboseOn()) Debug.logVerbose("[Set path/method]: " + eventPath + " / " + eventMethod, module);

Class[] paramTypes = new Class[] {HttpServletRequest.class, HttpServletResponse.class};

Debug.logVerbose("*[[Event invocation]]*", module);
Object[] params = new Object[] {request, response};

return invoke(eventPath, eventMethod, eventClass, paramTypes, params);
}

private String invoke(String eventPath, String eventMethod, Class eventClass, Class[] paramTypes, Object[] params) throws EventHandlerException {
if (eventClass == null) {
throw new EventHandlerException("Error invoking event, the class " + eventPath + " was not found");
}
if (eventPath == null || eventMethod == null) {
throw new EventHandlerException("Invalid event method or path; call initialize()");
}

Debug.logVerbose("[Processing]: JAVA Event", module);
try {
Method m = eventClass.getMethod(eventMethod, paramTypes);
String eventReturn = (String) m.invoke(null, params);

if (Debug.verboseOn()) Debug.logVerbose("[Event Return]: " + eventReturn, module);
return eventReturn;
} catch (java.lang.reflect.InvocationTargetException e) {
Throwable t = e.getTargetException();

if (t != null) {
Debug.logError(t, "Problems Processing Event", module);
throw new EventHandlerException("Problems processing event: " + t.toString(), t);
} else {
Debug.logError(e, "Problems Processing Event", module);
throw new EventHandlerException("Problems processing event: " + e.toString(), e);
}
} catch (Exception e) {
Debug.logError(e, "Problems Processing Event", module);
throw new EventHandlerException("Problems processing event: " + e.toString(), e);
}
}
}
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我是新手，能不能有高手幫忙解釋下，好多API我都不熟啊

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