30.2 Servlet_自启动Servlet特点，Servlet_Servlet线程安全问题_servlet自起线程

 Servlet_自启动Servlet特点

Servlet_Servlet线程安全问题

package ThreadSafeServlet07;
/**
 * 多个线程访问同一个资源时 线程安全问题
 */
 
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
 
public class ThreadSafeServlet01 extends HttpServlet {
    private PrintWriter pw;  //将printwrite定义到成员变量中,   当多个浏览器（多个线程）同时访问时容易出现抢占资源，如果把变量定义到成员变量记得实现线程同步
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req,resp);
    }
 
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String name = req.getParameter("name");
        pw = resp.getWriter();
 
        synchronized (this){  //使用synchrenized来实现多个线程同步
            try{
                Thread.sleep(5000);
                pw.println(name);
                pw.flush();
                pw.close();
            }catch(Exception e){
                e.printStackTrace();
            }
        }
    }
}