servlet3.0的问题
- Servlet3.0与Servlet2.5提供了三个新特性:
* 注解开发 ：方便
* 文件上传 ：有些API不是特别全.
* 异步请求 ：多线程的实现
注解开发：
注解的开发是的整个开发过程中不需要web.xml配置文件。
web层
Servlet @WebServlet("访问路径")
Filter @WebFilter("访问路径")
Listener @WebListener("访问路径")
service层
@WebService
文件上传：
这个上传过程是特别繁琐的，其中获取文件名字需要从发送过来的头部进行String的方法进行截取。使得整个过程繁琐；对于流的对接也不是特别友好。
使用fileUpload工具包来开发有特定的文件项的流的对接。整个开发过程大大节约了时间。
代码:
@WebServlet("/UploadServlet")
@MultipartConfig//表示文件上传注解
public class UploadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 接收普通数据:
request.setCharacterEncoding("UTF-8");
String filedesc = request.getParameter("filedesc");
System.out.println("文件描述"+filedesc);
// 接收文件:
Part part = request.getPart("upload");
long size = part.getSize();// 获得文件大小:
System.out.println("文件大小:"+size);
String name = part.getName();
System.out.println("文件表单中的name属性的名称"+name);
// 获得文件名:
String header = part.getHeader("Content-Disposition");
int idx = header.lastIndexOf("filename="");
String fileName = header.substring(idx+10, header.length()-1);
System.out.println("文件名:"+fileName);
// 获得文件内容:
InputStream is = part.getInputStream();
// 获得upload的路径:
String path = this.getServletContext().getRealPath("/upload");
OutputStream os = new FileOutputStream(path+"/"+fileName);
byte[] b = new byte[1024];
int len = 0;
while((len = is.read(b))!=-1){
os.write(b, 0, len);
}
is.close();
os.close();
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
异步：异步的实现其实是一个多线程。
/**
* 异步请求的Servlet
*/
@WebServlet(urlPatterns="/AsyncServlet",asyncSupported=true)
public class AsyncServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
AsyncContext context = request.startAsync(request, response);
context.start(new MyRunnable(context));
for(int i = 1;i<=10;i++){
System.out.println(i);
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
class MyRunnable implements Runnable{
private AsyncContext context;
public MyRunnable(AsyncContext context) {
this.context = context;
}
@Override
public void run() {
for(char i='a';i<='z';i++){
try {
context.getResponse().getWriter().println(i);
Thread.sleep(100);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}