JavaWeb中的request和response

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已于 2024-05-30 19:34:31 修改

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于 2024-05-30 17:20:48 首次发布

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在Java Web开发中，HttpServletRequest和HttpServletResponse是用于处理客户端请求和服务器响应的两个关键接口。它们提供了丰富的方法来处理和操控HTTP请求和响应。以下是这些接口的一些常见操作和示例。

`HttpServletRequest` 常见操作

获取请求参数

单个参数：

String paramValue = request.getParameter("paramName");

多个参数：

String[] paramValues = request.getParameterValues("paramName");

获取请求头信息

单个请求头：

String headerValue = request.getHeader("headerName");

所有请求头：

Enumeration<String> headerNames = request.getHeaderNames();
while (headerNames.hasMoreElements()) {
    String headerName = headerNames.nextElement();
    String headerValue = request.getHeader(headerName);
    // Process header
}

获取请求方法

String method = request.getMethod();  // GET, POST

获取请求URL和URI

String requestURI = request.getRequestURI();
StringBuffer requestURL = request.getRequestURL();

获取客户端IP地址

String clientIP = request.getRemoteAddr();

获取请求上下文路径

String contextPath = request.getContextPath();

获取Session对象

HttpSession session = request.getSession();

读取请求体数据（例如，处理POST请求的数据）

BufferedReader reader = request.getReader();
StringBuilder body = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
    body.append(line);
}
// body.toString() contains the request body

`HttpServletResponse` 常见操作

设置响应状态码

response.setStatus(HttpServletResponse.SC_OK);  // 200
response.setStatus(HttpServletResponse.SC_NOT_FOUND);  // 404

设置响应头

response.setHeader("Content-Type", "text/html");
response.setHeader("Cache-Control", "no-cache");

设置响应内容类型

response.setContentType("text/html;charset=UTF-8");

设置响应体内容

PrintWriter out = response.getWriter();
out.println("<html><body>Hello, World!</body></html>");
out.flush();

重定向

response.sendRedirect("http://www.example.com");

发送错误响应

response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Invalid request");

示例代码

以下是一个综合示例，展示了如何在Servlet中使用HttpServletRequest和HttpServletResponse：

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/example")
public class ExampleServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        // 获取请求参数
        String param = request.getParameter("param");
        
        // 设置响应内容类型
        response.setContentType("text/html;charset=UTF-8");
        
        // 设置响应头
        response.setHeader("Custom-Header", "value");
        
        // 获取响应输出流
        PrintWriter out = response.getWriter();
        
        // 写入响应内容
        out.println("<html>");
        out.println("<head><title>Example</title></head>");
        out.println("<body>");
        out.println("<h1>Parameter: " + param + "</h1>");
        out.println("</body>");
        out.println("</html>");
        
        out.flush();
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        // 读取请求体数据
        BufferedReader reader = request.getReader();
        StringBuilder body = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            body.append(line);
        }
        
        // 打印请求体
        System.out.println("Request Body: " + body.toString());
        
        // 设置响应状态码
        response.setStatus(HttpServletResponse.SC_OK);
        
        // 设置响应内容类型
        response.setContentType("application/json;charset=UTF-8");
        
        // 写入响应内容
        PrintWriter out = response.getWriter();
        out.println("{\"message\": \"Data received\"}");
        out.flush();
    }
}