Servlet学习--练习示例总结
醉了醉了。。本来想测试下Servlet生命周期的，然后调了好久的错误，还是没成功，不知道为什么不能这样做
贴上代码：
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LifeServlet extends HttpServlet{
private static final long serialVersionUID = 1L;
StringBuffer str;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
str.append("处理Servlet请求-1");
doPost(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
str.append("处理Servlet请求-2");
response.setCharacterEncoding("utf-8");
PrintWriter out;
out = response.getWriter();
out.println("<html>");
out.println("<head><title>fuck you</title></head>");
out.println(str);
out.println("</html>");
out.close();
}
@Override
public void destroy() {
str.append("销毁Servlet");
}
@Override
public void init() {
str.append("初始化Servlet");
}
}
我只是想不在控制台打印出来而已，要不要这样啊
另外测试了下客户端跳转request请求是不行的，服务端跳转都可以
贴上客户端跳转 request，session，application三种请求代码示例
import java.io.IOException;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class RedirectServlet extends HttpServlet{
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setAttribute("requestKey", "requestֵ");
HttpSession session=request.getSession();
session.setAttribute("sessionKey", "sessionֵ");
ServletContext application=this.getServletContext();
application.setAttribute("applicationKey", "applicationֵ");
response.sendRedirect("target.jsp");
}
}另外目标地址（target.jsp）的文件：<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>目标地址</h1>
request值：<%=request.getAttribute("requestKey") %><br/>
session值：<%=session.getAttribute("sessionKey") %><br/>
application值：<%=application.getAttribute("applicationKey") %><br/>
</body>
</html>OK，下面贴上服务器跳转对应三种请求的代码示例：
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class ForwardServlet extends HttpServlet{
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setAttribute("requestKey", "requestֵ");
HttpSession session=request.getSession();
session.setAttribute("sessionKey", "sessionֵ");
ServletContext application=this.getServletContext();
application.setAttribute("applicationKey", "applicationֵ");
RequestDispatcher rd=request.getRequestDispatcher("target.jsp");
rd.forward(request, response);
}
}
可以看出服务器端跳转只是 RequestDispatcher rd=request.getRequestDispatcher("target.jsp");
rd.forward(request, response); 和客户端的不同，所以个人理解也就是客户端跳转应该是服务器通过response返回给客户端，然后客户端对应跳转url
另外：
贴个比较好的理解
1.forward跳转：
a.服务器端跳转，地址栏不改变；
b.执行到跳转语句后马上无条件跳转，之后的代码不再执行(跳转之前一定要释放全部资源)；
c.request设置的属性在跳转后的页面仍可以使用；
d.使用<jsp:param name="参数名" value="参数值" />传递参数。
2.response跳转：
a.客户端跳转,地址栏改变；
b.所有代码执行完毕后跳转；
c.跳转后的页面不能使用上一个页面的request属性；
d.使用地址重写传递参数（response.sendRedirect("URL?参数名＝参数值")）。
说实话里面的细节我也不懂，知道有这么回事就行了
