Echo Web Framework

I have done a bit of Echo and Spring integration on this weekend and came up with the following two class, ContextLoaderEchoServer and EchoInstanceSupport that *knows* about Spring's WebApplicationContext. Hope this might comes in handy to others. If there are any better ways of doing it, kindly shared it (by posting through this thread). Thanks

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.BeanUtils;
import org.springframework.context.ApplicationContextException;
import org.springframework.util.StringUtils;
import org.springframework.web.context.ConfigurableWebApplicationContext;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;
import org.springframework.web.context.support.XmlWebApplicationContext;

import nextapp.echo.EchoInstance;
import nextapp.echoservlet.EchoServer;

/**
 * <pre>
 *  < servlet >
 *      < servlet-name > myEchoServer < /servlet-name >
 *      < servlet-class > org.huihoo.jfox.cms.echo.ContextLoaderEchoServer < /servlet-class >  
 *      < init-param > 
 *          < param-name > NAMESPACE_PARAM < /param-name > 
 *          < param-value > myEchoServer-servlet < /param-value > 
 *      < /init-param > 
 *      < init-param > 
 *          < param-name > CONTEXT_CONFIG_LOCATION_PARAM < /param-name > 
 *          < param-value > /WEB-INF/config1.xml,/WEB-INF/config2.xml,/WEB-INF/config3.xml < /param-value > 
 *      < /init-param > 
 *      < init-param > 
 *          < param-name > SERVLET_CONTEXT_PARAM < /param-name > 
 *          < param-value > myEchoServer-servlet-context < /param-value > 
 *      < /init-param > 
 *      < init-param > 
 *          < param-name > CONTEXT_CLASS_PARAM < /param-name > 
 *          < param-value > org.springframework.web.context.support.XmlWebApplicationContext < /param-value > 
 *      < /init-param > 
 *  < /servlet > 
 * </pre>
 * 
 * OR
 * 
 * <pre>
 * <servlet>
 *      <servlet-name>myEchoServer</servlet-name>
 *      <servlet-class>org.huihoo.jfox.cms.echo.ContextLoaderEchoServer</servlet-class>
 * </servlet>
 * </pre>
 * 
 * 
 * @author <a href="mailto:tm_jee@yahoo.co.uk">tmjee</a>
 * @version $Date$ $Revision$
 * @since 1.0
 */
public abstract class ContextLoaderEchoServer extends EchoServer {

    /**
     * Suffix for WebApplicationContext namespaces. If this 
     * {@link ContextLoaderEchoServer} is given the name "echoserver" in a context, 
     * the namespace used by this {@link ContextLoaderEchoServer} will
     * resolve to "echoserver-servlet".
     */
	public static final String DEFAULT_NAMESPACE_SUFFIX = "-servlet";
    
    /**
     * The default context class for ContextLoaderPlugIn (XmlWebApplicationContext).
     * @see org.springframework.web.context.support.XmlWebApplicationContext
     */
	public static final Class DEFAULT_CONTEXT_CLASS = XmlWebApplicationContext.class;
    
    /**
     * Prefix for the ServletContext attribute for the WebApplicationContext.
     * The completion is the this class {@link ContextLoaderEchoServer} plus ".CONTEXT".
     */
	public static final String DEFAULT_SERVLET_CONTEXT_PREFIX = ContextLoaderEchoServer.class.getName()+".CONTEXT";

	/**
     * Servlet Context Param to set the WebApplicationContext's namespace, 
     * default to 'NAMESPACE_PARAM'.
  */
    public static final String NAMESPACE_PARAM = "NAMESPACE_PARAM";
    /**
     * Servlet Context Param to set the WebApplicationContext's config location, 
     * default to 'CONTEXT_CONFIG_LOCATION_PARAM'.
     */
    public static final String CONTEXT_CONFIG_LOCATION_PARAM = "CONTEXT_CONFIG_LOCATION_PARAM";
    /**
     * Servlet Context Param to set the WebApplicationContext's servlet context param,
     * default to 'SERVLET_CONTEXT_PARAM'.
     */
    public static final String SERVLET_CONTEXT_PARAM = "SERVLET_CONTEXT_PARAM";
    /**
     * Servlet Context Param to set the WebApplicationContext's Context Class, default
     * to 'CONTEXT_CLASS_PARAM'
     */
    public static final String CONTEXT_CLASS_PARAM = "CONTEXT_CLASS_PARAM";
    
    
    private static final Log log = LogFactory.getLog(ContextLoaderEchoServer.class);
    
    private String _namespace = null;
    private String _contextConfigLocation = null;
    private String _servletContextParam = null;
    private Class _contextClass = null;
    private WebApplicationContext _webApplicationContext = null;
    
    private EchoInstanceSupport _echoInstanceSupport = null;
    private ServletConfig _servletConfig = null;
    private ServletContext _servletContext = null;
    
    /**
     * Initialize the WebApplicationContext.
     */
    public void init(ServletConfig servletConfig) throws ServletException {
        log.info("start initializing "+getClass().getName());
        long startTime = System.currentTimeMillis();
        
        super.init(servletConfig);
    	initWebApplicationContext(servletConfig);
        
        long doneTime = System.currentTimeMillis();
        long duration = doneTime - startTime;
        log.info("done initalizing "+getClass().getName()+" in "+duration+" ms");
    }
    
    
    
	/**
  * @see nextapp.echoservlet.EchoServer#newInstance()
  */
	public EchoInstance newInstance() {
  _echoInstanceSupport =  newEchoInstanceSupport(_webApplicationContext);
        return _echoInstanceSupport;
	}
    
    /**
     * To be implmented by subclass the same way as {@link EchoServer#newInstance()}
     * except that now it has a {@link WebApplicationContext}. Subclass should 
     * return an instance of {@link EchoInstanceSupport} which has a single constructor
     * that takes in a {@link WebApplicationContext}.
     * 
     * @param webApplicationContext
     * @return EchoInstanceSupport
     */
    public abstract EchoInstanceSupport newEchoInstanceSupport(
            WebApplicationContext webApplicationContext);
    
    
    
    // protected ==========================================
    protected void initWebApplicationContext(ServletConfig servletConfig) {
        _servletContext = servletConfig.getServletContext();
        _servletConfig = servletConfig;
        
        WebApplicationContext rootWebApplicationContext = 
            WebApplicationContextUtils.getRequiredWebApplicationContext(_servletContext);
        
        if (getContextConfigLocation() == null) {
        	// no child context config location specified, use the root webApplicationContext
            _webApplicationContext = rootWebApplicationContext;
        }
        else {
            _webApplicationContext = createWebApplicationContext(rootWebApplicationContext);
            
            // store Context in ServletContext
            _servletContext.setAttribute(getServletContextParam(), _webApplicationContext);
        }
    }
    
    protected ConfigurableWebApplicationContext createWebApplicationContext(
            WebApplicationContext rootWebApplicationContext) {
         try {
            Class contextClazz = getContextClass();
            if (! ConfigurableWebApplicationContext.class.isAssignableFrom(contextClazz)) {
                throw new ApplicationContextException(
                        "Fatal initialization error in "+getClass().getName()+" '" + getServletName() +
                        "' : custom WebApplicationContext class [" + contextClazz+
                        "] is not of type ConfigurableWebApplicationContext");
            }
            ConfigurableWebApplicationContext cwac = 
                (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClazz);
            
            // init cwac
            cwac.setParent(rootWebApplicationContext);
            cwac.setNamespace(getNamespace());
            cwac.setServletContext(_servletConfig.getServletContext());
            cwac.setConfigLocations(StringUtils.tokenizeToStringArray(
                    getContextConfigLocation(), 
                    ConfigurableWebApplicationContext.CONFIG_LOCATION_DELIMITERS, 
                    true, true));
            cwac.refresh();
            return cwac;
        }
        catch(ClassNotFoundException e) {
            log.error("Exception while initailizing web application context ", e);
            throw new ApplicationContextException("Exception while initailizing web application context ", e);
        }
    }
    
    
    // private ===========================================
    private String getNamespace() {
        if (_namespace == null) {
        	// first time
        	String param = _servletConfig.getInitParameter(NAMESPACE_PARAM);
        	if (param == null || param.trim().length() <= 0) {
          _namespace = _servletConfig.getServletName()+DEFAULT_NAMESPACE_SUFFIX;
        	}
            else {
            	_namespace = param;
            }
        }
    	return _namespace;
    }
    
    private String getContextConfigLocation() {
        if (_contextConfigLocation == null) {
            String param = _servletConfig.getInitParameter(CONTEXT_CONFIG_LOCATION_PARAM);
            if (param != null && param.trim().length() > 0) {
            	_contextConfigLocation = param;
            }
        }
    	return _contextConfigLocation;
    }
    
    private Class getContextClass() throws ClassNotFoundException {
    	if (_contextClass == null) { // first time
            String param = _servletConfig.getInitParameter(CONTEXT_CLASS_PARAM);
            if (param == null || param.trim().length() <= 0) {
            	_contextClass = DEFAULT_CONTEXT_CLASS;
            }
            else {
                _contextClass = Class.forName(param, true, Thread.currentThread().getContextClassLoader());
            }
        }
        return _contextClass;
    }
    
    private String getServletContextParam() {
    	if (_servletContextParam == null) {
      // first time
            String param = _servletConfig.getInitParameter(SERVLET_CONTEXT_PARAM);
            if (param == null || param.trim().length() <= 0) {
                _servletContextParam = DEFAULT_SERVLET_CONTEXT_PREFIX+ _echoInstanceSupport.getClass().getName();
            }
            else {
            	_servletContextParam = param;
            }
        }
        return _servletContextParam;
    }
}

import org.springframework.web.context.WebApplicationContext;

import nextapp.echo.EchoInstance;

/**
 * @author <a href="mailto:tm_jee@yahoo.co.uk">tmjee</a>
 * @version $Date$ $Revision$
 * @since 1.0
 */
public abstract class EchoInstanceSupport extends EchoInstance {

    private WebApplicationContext _webApplicationContext;
    
    public EchoInstanceSupport(WebApplicationContext webApplicationContext) {
    	_webApplicationContext = webApplicationContext;
    }
    
	protected WebApplicationContext getWebApplicationContext() {
  return _webApplicationContext;
    }
}

regards
tmjee