1.功能：设置响应消息
1. 设置响应行
1. 格式：HTTP/1.1 200 ok
2. 设置状态码：setStatus(int sc)
2. 设置响应头：setHeader(String name, String value)
3. 设置响应体：
使用步骤：
1. 获取输出流
字符输出流：PrintWriter getWriter()
字节输出流：ServletOutputStream getOutputStream()
2. 使用输出流，将数据输出到客户端浏览器
2.案例
2.1 完成重定向
重定向：资源跳转的方式
package cn.itcast.web.servlet; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; /** * 重定向 */ @WebServlet("/ResponseDemo1") public class ResponseDemo1 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("demo1........"); //访问/ResponseDemo1，会自动跳转到/ResponseDemo2资源 //1. 设置状态码为302 response.setStatus(302); //2.设置响应头location response.setHeader("location","/day15Response/ResponseDemo2"); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
package cn.itcast.web.servlet; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/ResponseDemo2") public class ResponseDemo2 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("demo2222222........"); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
另外一种简单的方法
package cn.itcast.web.servlet; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; /** * 重定向 */ @WebServlet("/ResponseDemo1") public class ResponseDemo1 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("demo1........"); //访问/ResponseDemo1，会自动跳转到/ResponseDemo2资源 request.setAttribute("msg","response"); //动态获取虚拟目录 String contextPath = request.getContextPath(); System.out.println(contextPath); //简单的重定向方法 response.sendRedirect(contextPath+"/ResponseDemo2"); //response.sendRedirect("http://www.itcast.cn"); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
package cn.itcast.web.servlet; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/ResponseDemo2") public class ResponseDemo2 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("demo2222222........"); Object msg = request.getAttribute("msg"); System.out.println(msg); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
重定向的特点:redirect
1. 地址栏发生变化
2. 重定向可以访问其他站点(服务器)的资源
3. 重定向是两次请求。不能使用request对象来共享数据
转发的特点：forward
1. 转发地址栏路径不变
2. 转发只能访问当前服务器下的资源
3. 转发是一次请求，可以使用request对象来共享数据
forward 和 redirect 区别
路径写法：
1. 路径分类
1. 相对路径：通过相对路径不可以确定唯一资源
如：./index.html
不以/开头，以.开头路径
规则：找到当前资源和目标资源之间的相对位置关系
./：当前目录
../:后退一级目录
2. 绝对路径：通过绝对路径可以确定唯一资源
如：http://localhost/day15/responseDemo2 /day15/responseDemo2
以/开头的路径
规则：判断定义的路径是给谁用的？判断请求将来从哪儿发出
给客户端浏览器使用：需要加虚拟目录(项目的访问路径)
* 建议虚拟目录动态获取：request.getContextPath()
* <a> , <form> 重定向...
给服务器使用：不需要加虚拟目录
* 转发路径
2.2 服务器输出字符数据到浏览器
步骤：
1. 获取字符输出流
2. 输出数据
package cn.itcast.web.servlet; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.io.PrintWriter; @WebServlet("/ResponseDemo4") public class ResponseDemo4 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取流对象之前，设置流的默认编码：ISO-8859-1 设置为：GBK // response.setCharacterEncoding("utf-8"); //告诉浏览器，服务器发送的消息体数据的编码。建议浏览器使用该编码解码 //response.setHeader("content-type","text/html;charset=utf-8"); //简单的形式，设置编码 response.setContentType("text/html;charset=utf-8"); //1.获取字符输出流 PrintWriter pw = response.getWriter(); //2.输出数据 //pw.write("<h1>hello response</h1>"); pw.write("你好啊啊啊 response"); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
注意：
乱码问题：
1. PrintWriter pw = response.getWriter();获取的流的默认编码是ISO-8859-1
2. 设置该流的默认编码
3. 告诉浏览器响应体使用的编码
//简单的形式，设置编码，是在获取流之前设置
response.setContentType("text/html;charset=utf-8");
3. 服务器输出字节数据到浏览器
* 步骤：
1. 获取字节输出流
2. 输出数据
4. 验证码
1. 本质：图片
2. 目的：防止恶意表单注册