gwt(google web toolkit) 跟 spring 在一起使用列子

package org.spring4gwt.server;

import javax.servlet.http.HttpServletRequest;

import org.apache.log4j.Logger;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

import com.google.gwt.user.client.rpc.IncompatibleRemoteServiceException;
import com.google.gwt.user.client.rpc.RemoteService;
import com.google.gwt.user.client.rpc.SerializationException;
import com.google.gwt.user.server.rpc.RPC;
import com.google.gwt.user.server.rpc.RPCRequest;
import com.google.gwt.user.server.rpc.RemoteServiceServlet;

@SuppressWarnings("serial")
public class SpringGwtRemoteServiceServlet extends RemoteServiceServlet {

private static final Logger LOG = Logger.getLogger(SpringGwtRemoteServiceServlet.class);

// servlet的初始化方法
@Override
public void init() {
if (LOG.isDebugEnabled()) {
LOG.debug("Spring GWT service exporter deployed");
}
}

/**
* RemoteServiceServlet 中调用的方法，处理给定的request信息
*/
@Override
public String processCall(String payload) throws SerializationException {
try {
// 取出要被调用的bean实例
Object handler = getBean(getThreadLocalRequest());
// 对请求进行解码, 获取所有的请求信息, 主要是方法和参数
RPCRequest rpcRequest = RPC.decodeRequest(payload, handler.getClass(), this);
onAfterRequestDeserialized(rpcRequest);
if (LOG.isDebugEnabled()) {
LOG.debug("Invoking " + handler.getClass().getName() + "." + rpcRequest.getMethod().getName());
}
// 使用反射方式调用实例对象的方法, 返回调用结果
return RPC.invokeAndEncodeResponse(handler, rpcRequest.getMethod(), rpcRequest.getParameters(), rpcRequest
.getSerializationPolicy());
} catch (IncompatibleRemoteServiceException ex) {
log("An IncompatibleRemoteServiceException was thrown while processing this call.", ex);
return RPC.encodeResponseForFailure(null, ex);
}
}

/**
* 基于request URL进行的获取实例bean的操作
* 比如说：请求结尾时/myService，那么我们就会将spring中的bean实例为myService
*
* @param request
* @return handler bean
*/
protected Object getBean(HttpServletRequest request) {
String service = getService(request);
// 从spring中的applicationContext中取出bean
Object bean = getBean(service);
if (!(bean instanceof RemoteService)) {
throw new IllegalArgumentException("Spring bean is not a GWT RemoteService: " + service + " (" + bean + ")");
}
if (LOG.isDebugEnabled()) {
LOG.debug("Bean for service " + service + " is " + bean);
}
return bean;
}

/**
* 解析bean的名称，通过request来解析
* 如/spring 会被解析为 spring
* @param request
* @return bean name
*/
protected String getService(HttpServletRequest request) {
// 获得url
String url = request.getRequestURI();
// 对取最后一个"/"后面的内容
String service = url.substring(url.lastIndexOf("/") + 1);
if (LOG.isDebugEnabled()) {
LOG.debug("Service for URL " + url + " is " + service);
}
return service;
}

/**
* 在当前webApplicationContext中取出bean的实例
*
* @param name
* bean name
* @return the bean
*/
protected Object getBean(String name) {
// 调用spring自带的utils
WebApplicationContext applicationContext = WebApplicationContextUtils
.getWebApplicationContext(getServletContext());
if (applicationContext == null) {
throw new IllegalStateException("No Spring web application context found");
}
if (!applicationContext.containsBean(name)) {
{
throw new IllegalArgumentException("Spring bean not found: " + name);
}
}
// 获取bean实例
return applicationContext.getBean(name);
}
}