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DWR is easy Ajax for Java. It makes it simple to call Java code directly from Javascript. It gets rid of almost all the boilerplate code between the web browser and your Java code. This version 4.0.2 works with Jakarta Servlet 4.0.2.

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package org.directwebremoting.create;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import org.directwebremoting.extend.AbstractCreator;
import org.directwebremoting.extend.Creator;
import org.directwebremoting.util.LocalUtil;

/**
 * A creator that attempts to grab an instance of a static/singleton class.
 * @author David Marginian [david at butterdev dot com]
 */
public class StaticCreator extends AbstractCreator implements Creator
{
    /**
     * What sort of class do we create?
     * @param classname The name of the class
     */
    public void setClass(String classname)
    {
        try
        {
            clazz = LocalUtil.classForName(classname);
            if (getJavascript() == null)
            {
                setJavascript(clazz.getSimpleName());
            }
        }
        catch (ExceptionInInitializerError ex)
        {
            throw new IllegalArgumentException("Error loading class: " + classname, ex);
        }
        catch (ClassNotFoundException ex)
        {
            throw new IllegalArgumentException("Class not found: " + classname, ex);
        }
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.Creator#getType()
     */
    public Class getType()
    {
        return clazz;
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.Creator#getInstance()
     */
    public Object getInstance() throws InstantiationException
    {
        try
        {
            Method getInstanceMethod = clazz.getDeclaredMethod(instanceMethodName, new Class[] {});
            return getInstanceMethod.invoke(null, new Object[] {});
        }
        catch (IllegalAccessException ex)
        {
            throw new InstantiationException("Illegal Access to default constructor on " + clazz.getName());
        }
        catch (NoSuchMethodException ex)
        {
            throw new InstantiationException("The getInstance method specified " + instanceMethodName + " does not exist for " + clazz.getName());
        }
        catch (InvocationTargetException ex)
        {
            throw new InstantiationException("An exception occurred while calling the getInstanceMethod " + instanceMethodName + " on " + clazz.getName());
        }
    }

    /**
     * Retrieves name of the method that will be called to retrieve the static instance of this class.
     * @return the getInstanceMethodName
     */
    public String getInstanceMethodName()
    {
        return instanceMethodName;
    }

    /**
     * Sets the name of the method that will be called to retrieve the static instance of this class.
     * @param instanceMethodName the new getInstanceMethodName
     */
    public void setInstanceMethodName(String instanceMethodName)
    {
        this.instanceMethodName = instanceMethodName;
    }

    /**
     * Sets the class name to create.
     * @param className The name of the class to create
     */
    public void setClassName(String className)
    {
        setClass(className);
    }

    /**
     * Gets the name of the class to create.
     * @return The name of the class to create
     */
    public String getClassName()
    {
        return getType().getName();
    }

    /**
     * The type of the class that we are creating
     */
    private Class clazz;

    /**
     * The name of the method that will be called to retrieve the static instance of this class.
     */
    private String instanceMethodName = "getInstance";
}