DWR的简单实现

前段时间给一个同学做一个毕业设计，由于要求只能用jsp/servlet实现。用惯了dwr框架，于是自己模仿了下DWR的实现:

简单的模仿了下DWR框架的实现:

这是MyDwrServlet.java源码:

package com.xcy.core.web.dwr;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.lang.reflect.Method;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

/**
* @author Siuon
*
*/
@SuppressWarnings("all")
public class MyDWRServlet extends HttpServlet{
/**
* serialVersionUID
*/
private final long serialVersionUID = 1L;
private final String RT = "\r\n";
private final String TAB = "\t";
private String CONTEXT_PATH = null;
private HashMap<String,JSClassMapping> jsAndClassMapping = new HashMap<String,JSClassMapping>();
private StringBuffer engineFileContent;

public MyDWRServlet(){
//System.out.println("MyDWRServlet Constructor");
}

@Override
public void init() throws ServletException {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = null;
try {
builder = factory.newDocumentBuilder();
Document document = builder.parse(new File(this.getServletContext().getRealPath("/WEB-INF/mydwr.xml")));
Element root = document.getDocumentElement();
Element allow = (Element)root.getElementsByTagName("allow").item(0);
NodeList creates = allow.getElementsByTagName("create");
for (int i = 0; i < creates.getLength(); i++) {
Element create = (Element)creates.item(i);
String javascript = create.getAttribute("javascript");
String clazz = create.getAttribute("class");
Class c = Class.forName(clazz);
jsAndClassMapping.put(javascript, new JSClassMapping(javascript, c, c.newInstance()));
}

BufferedReader reader = new BufferedReader(new InputStreamReader(MyDWRServlet.class.getResourceAsStream("engine.js")));
String line = null;
engineFileContent = new StringBuffer();
while((line=reader.readLine())!=null){
engineFileContent.append(line+RT);
}
reader.close();
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
CONTEXT_PATH = req.getContextPath()+"/mydwr/interface/";
String requestURI = req.getRequestURI();
if(!requestURI.endsWith(".js")) return;
String jsName = requestURI.substring(CONTEXT_PATH.length(), requestURI.length()-3);
if("engine".equals(jsName)){
write(resp, engineFileContent.toString());
return;
}

JSClassMapping jsClassMapping = jsAndClassMapping.get(jsName);
if(jsClassMapping==null) return;

try {
if(jsClassMapping.getJsFileContent()==null){
Class c = jsClassMapping.getClazz();
Type[] types = c.getGenericInterfaces();
if(types.length==0){
throw new RuntimeException(c.getClass()+"必须实现一个接口!");
}
Class intface = (Class)types[0];
Method[] methods = intface.getDeclaredMethods();

StringBuffer jsFileContent = new StringBuffer("var mydwr = null;"+RT);
jsFileContent.append("if(mydwr==null){mydwr=new MyDWR();};"+RT);
jsFileContent.append("var "+jsName+" = null;"+RT);
jsFileContent.append("if(null=="+jsName+"){"+jsName+"={};};"+RT);
StringBuffer functionBody = new StringBuffer();
for (int i = 0; i < methods.length; i++) {
functionBody.setLength(0);
Method method = methods[i];
functionBody.append(jsName+"."+methods[i].getName()+"=function(");
Class[] params = method.getParameterTypes();
StringBuffer paramArrayStr = new StringBuffer("[");
for (int j = 0; j < params.length; j++) {
if(j==0){
functionBody.append("p"+j);
paramArrayStr.append("p"+j);
}else{
functionBody.append(",p"+j);
paramArrayStr.append(",p"+j);
}
}
paramArrayStr.append("];");
if(params.length!=0){
functionBody.append(",");
}
functionBody.append("callback){"+RT);
functionBody.append(TAB+"var params = "+paramArrayStr+RT);
functionBody.append(TAB+"mydwr.request('"+CONTEXT_PATH+"','"+jsName+"','"+method.getName()+"',params,callback);"+RT);
functionBody.append("}"+RT);
jsFileContent.append(functionBody);
}
jsClassMapping.setJsFileContent(jsFileContent);
}
} catch (SecurityException e) {
e.printStackTrace();
}finally{
if(jsClassMapping.getJsFileContent()!=null){
write(resp,jsClassMapping.getJsFileContent().toString());
}
}
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("UTF-8");
Map<String,Object> params = (Map<String,Object>)req.getParameterMap();
List<String> paramValues = new ArrayList<String>();
for (int i = 0; i < params.size(); i++) {
paramValues.add(req.getParameter("p"+i));
}
String clazzAndMethod = req.getRequestURI().substring(CONTEXT_PATH.length());
String className = clazzAndMethod.split("!")[0];
String methodName = clazzAndMethod.split("!")[1];
JSClassMapping jsClassMapping = jsAndClassMapping.get(className);
Method[] methods = jsClassMapping.getClazz().getDeclaredMethods();
Method method = null;
for (int i = 0; i < methods.length; i++) {
if(methods[i].getName().equals(methodName)){
method = methods[i];
break;
}
}
Class[] types = method.getParameterTypes();
Object[] values = new Object[paramValues.size()];
for (int i = 0; i < types.length; i++) {
if("Integer".equals(types[i].getSimpleName())){
values[i] = Integer.parseInt(paramValues.get(i));
}else if("Double".equals(types[i].getSimpleName())){
values[i] = Double.parseDouble(paramValues.get(i));
}else{
values[i] = paramValues.get(i);
//其它类型当String处理.
}
}
Object result = null;
try {
result = method.invoke(jsClassMapping.getObjct(), values);
} catch (Exception e) {
result = e.getMessage();
e.printStackTrace();
}
processResult(resp,result);
}

/**
* 处理调用方法后的结果,针对不同类型返回值,分别处理。
* @param resp
* @param result
* @throws IOException
*/
private void processResult(HttpServletResponse resp,Object result) throws IOException {
StringBuffer temp = new StringBuffer("[");
if(result instanceof Object[]){
Object[] objs = (Object[])result;
for (int i = 0; i < objs.length; i++) {
temp.append("'"+objs[i]+"'");
if(i!=objs.length-1){
temp.append(",");
}
}
temp.append("]");
result = temp.toString();
}else if(result instanceof List){
List list = (List)result;
for (int i = 0; i < list.size(); i++) {
Object el = list.get(i);
if(el instanceof Map){
temp.append("{");
Map map = (Map)el;
Set<Map.Entry<Object,Object>> sets = map.entrySet();
for(Map.Entry<Object,Object> entry : sets){
Object value = entry.getValue()==null?"":entry.getValue();
temp.append("'"+entry.getKey()+"':'" + value +"',");
}
temp.replace(temp.length()-1, temp.length(), "}");;
}else{
temp.append("'"+list.get(i)+"'");
}
if(i!=list.size()-1){
temp.append(",");
}
}
result = temp.append("]");
}else if(result instanceof Map){
temp = new StringBuffer("{");
Map map = (Map)result;
Set<Map.Entry<Object,Object>> sets = map.entrySet();
for(Map.Entry<Object,Object> entry : sets){
Object value = entry.getValue()==null?"":entry.getValue();
temp.append("'"+entry.getKey()+"':'" + value +"',");
}
temp.replace(temp.length()-1, temp.length(), "}");;
result = temp.toString();
}else{
//其它类型一律作为String
result = "'"+result+"'";
}
write(resp,result.toString());
}

private void write(HttpServletResponse resp,String content) throws IOException{
OutputStream os = resp.getOutputStream();
os.write(content.getBytes("UTF-8"));
os.flush();
os.close();
}

}

engine.js

function MyDWR(){}
MyDWR.prototype.request = function(context,className,methodName,params,callback){
var queryContent = "";
if(params.length){
for(var i=0;i<params.length;i++){
if(i==0){
queryContent+="p"+i+"="+params[i];
}else{
queryContent+="&p"+i+"="+params[i];
}
}
}
var xmlHttpRequest;
// 生成ajax引擎
if (window.XMLHttpRequest) { // Mozilla 浏览器
xmlHttpRequest = new XMLHttpRequest();
} else if (window.ActiveXObject) { // IE浏览器
try {
xmlHttpRequest = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
xmlHttpRequest = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {
}
}
}
xmlHttpRequest.open("POST",context+className+"!"+methodName,true);
xmlHttpRequest.onreadystatechange = function(){
if (xmlHttpRequest.readyState == 4) { // 判断对象状态
if (xmlHttpRequest.status == 200) { // 信息已经成功返回，开始处理信息
//prompt("DWR Return:",xmlHttpRequest.responseText);
var datas = undefined;
try{
eval("datas = "+xmlHttpRequest.responseText+";");
}catch(e){
alert("DWR Error:"+e.message);
datas = {};
}
callback.success(datas);
} else { // 页面不正常
eval("var datas = "+xmlHttpRequest.responseText+";");
callback.errorHandler(datas);
}
}
};
xmlHttpRequest.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
xmlHttpRequest.send(queryContent);
}
MyDWR.prototype.hello=function(){
alert("Hello MyDWR");
}

源码下载地址:

MyDwr源码下载