JavaWeb中HttpResponse和HttpRequest如何使用，針對這個問題，這篇文章詳細介紹了相對應的分析和解答，希望可以幫助更多想解決這個問題的小伙伴找到更簡單易行的方法。
在創建Servlet時會覆蓋service()方法，或doGet()/doPost(),這些方法都有兩個參數，一個為代表請求的request和代表響應response。service方法中的response的類型是ServletResponse，而doGet/doPost方法的response的類型是HttpServletResponse，HttpServletResponse是ServletResponse的子接口，功能和方法更加強大。
響應頭有很多這里只介紹常用的。
在瀏覽器可以按F12 抓包看響應頭、請求頭、具體的可以再查。
設置響應的狀態碼
/**
* @Author: crush
* @Date: 2021-05-09 19:35
* version 1.0
*/
@WebServlet("/test3")
public class HttpResponseTest3 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("設置狀態碼,前臺通過判斷狀態碼，來判斷請求是否成功");
resp.setStatus(404);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}測試
刷新 跳轉頁面
/**
* @Author: crush
* @Date: 2021-05-09 19:35
* version 1.0
*/
@WebServlet("/test4")
public class HttpResponseTest4 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 設置響應頭 每1秒自動刷新
System.out.println("設置響應頭 每1秒自動刷新");
resp.setHeader("Refresh", "1");
//定時跳轉 3秒后將自動跳轉
// resp.setHeader("Refresh","3;URL=hello.jsp");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}測試
/**
* response
* @author Adimi
*/
@WebServlet("/test4")
public class ResponseTest4 extends HttpServlet {
private static Integer id=1;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setHeader("Refresh","1");
PrintWriter writer = response.getWriter();
id++;
writer.print("id==>"+id);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}/**
* @Author: crush
* @Date: 2021-05-09 19:35
* version 1.0
*/
@WebServlet("/test1")
public class HttpResponseTest1 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 解決中文亂碼問題
// 設置響應頭
// 設置字符編碼 resp.setCharacterEncoding("UTF-8");
// 設置響應內容以什么格式展示到頁面 什么編碼格式 包含了設置字符編碼
resp.setContentType("text/html;charset=utf-8");
PrintWriter writer = resp.getWriter();
writer.print("中國,你好?。?！");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}測試
/**
* 重定向
* @Author: crush
* @Date: 2021-05-09 19:35
* version 1.0
*/
@WebServlet("/test5")
public class HttpResponseTest5 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.sendRedirect("hello.jsp");
// resp.setHeader("location","www.baidu.com"); 通過設置響應頭轉發
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}/**
* 重定向
* @Author: crush
* @Date: 2021-05-09 19:35
* version 1.0
*/
@WebServlet("/test5")
public class HttpResponseTest5 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// resp.sendRedirect("hello.jsp");
req.getRequestDispatcher("hello.jsp").forward(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}獲取路徑資源
String path=this.getServletContext().getRealPath("WEB-INF\\classes\\8.jpg");讀取資源
FileInputStream fileInputStream=new FileInputStream(path);
獲取到文件名，路徑在電腦上保存的形式是 \ \
String fileName=path.substring(path.lastIndexOf("\\")+1);設置消息頭告訴瀏覽器，我要下載1.png這個圖片 設置編碼
resp.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName, "UTF-8"));把讀取到的內容回送給瀏覽器
int len=0;
byte[] bytes=new byte[1024];
// ServletOutputStream 提供用于將二進制數據發送到客戶端的輸出流
ServletOutputStream servletOutputStream=resp.getOutputStream();
while((len=fileInputStream.read(bytes))>0) {
servletOutputStream.write(bytes,0,len);
}關閉資源
servletOutputStream.close(); fileInputStream.close();
注：8.jpg 放在我的resources 文件夾下 但是這里需要寫的是編譯完8.jpg存放的位置
具體代碼
/**
* @Author: crush
* @Date: 2021-05-09 19:40
* version 1.0
*/
@WebServlet("/down")
public class ResponseDownFile extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//獲取路徑資源
String path=this.getServletContext().getRealPath("WEB-INF\\classes\\8.jpg");
//讀取資源
FileInputStream fileInputStream=new FileInputStream(path);
//獲取到文件名，路徑在電腦上保存的形式是\\
String fileName=path.substring(path.lastIndexOf("\\")+1);
//設置消息頭告訴瀏覽器，我要下載1.png這個圖片
// 該方式文件名為中文時會亂碼
//防止中文亂碼
resp.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName, "UTF-8"));
//把讀取到的內容回送給瀏覽器
int len=0;
byte[] bytes=new byte[1024];
ServletOutputStream servletOutputStream=resp.getOutputStream();
while((len=fileInputStream.read(bytes))>0) {
servletOutputStream.write(bytes,0,len);
}
// 關閉資源
servletOutputStream.close();
fileInputStream.close();
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}我們在創建Servlet時會覆蓋service()方法，或doGet()/doPost(),這些方法都有兩個參數，一個為代表請求的request和代表響應response。service（）方法中寫了根據請求方式的不同調用doget()和dopost().
service方法中的request的類型是ServletRequest，而doGet/doPost方法的request類型HttpServletRequest，HttpServletRequest是ServletRequest的子接口，功能和方法更加強大.
/**
* @Author: crush
* @Date: 2021-05-11 16:52
* version 1.0
*/
@WebServlet("/request1")
public class RequestTest1 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 這里是請求的參數名 必須是同名的
String username = req.getParameter("username");
String password = req.getParameter("password");
PrintWriter writer = resp.getWriter();
writer.print("<h2>"+username+":"+password+"</h2>");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 設置請求的編碼 不然會亂碼
req.setCharacterEncoding("utf-8");
Enumeration<String> names = req.getParameterNames();
while (names.hasMoreElements()) {
String name = (String) names.nextElement();
String[] values = req.getParameterValues(name);
System.out.println(name+":"+ Arrays.toString(values));
}
}/**
* @Author: crush
* @Date: 2021-05-11 16:52
* version 1.0
*/
@WebServlet("/request3")
public class RequestTest3 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 獲得請求的url
StringBuffer requestURL = req.getRequestURL();
System.out.println("請求的URL===>"+requestURL);
// 獲得請求的Servlet的路徑
String path = req.getServletPath();
System.out.println("請求的Servlet的路徑===>"+path);
//返回發出此請求的HTTP方法的名稱，例如GET，POST或PUT
String method = req.getMethod();
System.out.println("返回發出此請求的HTTP方法的名稱==>"+method);
//返回發送請求的客戶端或最后一個代理的Internet協議（IP）地址
String remoteAddr = req.getRemoteAddr();
System.out.println("remoteAddr==>"+remoteAddr);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}/**
* @Author: crush
* @Date: 2021-05-11 16:52
* version 1.0
*/
@WebServlet("/request2")
public class RequestTest2 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 訪問request2 轉發到 request4去
req.getRequestDispatcher("/request4").forward(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}request對象也是一個存儲數據的區域對象，所以也具有如下方法：
setAttribute(String name, Object o)
getAttribute(String name)
removeAttribute(String name)
創建：啟動web應用程序的時候創建
銷毀：關閉web應用程序的時候銷毀
域的作用范圍：整個web應用的啟動周期
創建：訪問時創建request
銷毀：響應結束request銷毀
域的作用范圍：一次請求中
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