Httpservletresponse java send error

Httpservletresponse java send error

Provides a convenient implementation of the HttpServletResponse interface that can be subclassed by developers wishing to adapt the response from a Servlet. This class implements the Wrapper or Decorator pattern. Methods default to calling through to the wrapped response object.

Since: Servlet 2.3 Author: Various See Also: HttpServletResponse

HttpServletResponseWrapper

Throws: java.lang.IllegalArgumentException — if the response is null

addCookie

Specified by: addCookie in interface HttpServletResponse Parameters: cookie — the Cookie to return to the client

Specified by: containsHeader in interface HttpServletResponse Parameters: name — the header name Returns: true if the named response header has already been set; false otherwise

encodeURL

Specified by: encodeURL in interface HttpServletResponse Parameters: url — the url to be encoded. Returns: the encoded URL if encoding is needed; the unchanged URL otherwise.

encodeRedirectURL

Specified by: encodeRedirectURL in interface HttpServletResponse Parameters: url — the url to be encoded. Returns: the encoded URL if encoding is needed; the unchanged URL otherwise. See Also: HttpServletResponse.sendRedirect(java.lang.String) , HttpServletResponse.encodeUrl(java.lang.String)

encodeUrl

The default behavior of this method is to call encodeUrl(String url) on the wrapped response object.

Specified by: encodeUrl in interface HttpServletResponse Parameters: url — the url to be encoded. Returns: the encoded URL if encoding is needed; the unchanged URL otherwise.

encodeRedirectUrl

The default behavior of this method is to return encodeRedirectUrl(String url) on the wrapped response object.

Specified by: encodeRedirectUrl in interface HttpServletResponse Parameters: url — the url to be encoded. Returns: the encoded URL if encoding is needed; the unchanged URL otherwise.

sendError

Specified by: sendError in interface HttpServletResponse Parameters: sc — the error status code msg — the descriptive message Throws: java.io.IOException — If an input or output exception occurs

sendError

Specified by: sendError in interface HttpServletResponse Parameters: sc — the error status code Throws: java.io.IOException — If an input or output exception occurs

sendRedirect

Specified by: sendRedirect in interface HttpServletResponse Parameters: location — the redirect location URL Throws: java.io.IOException — If an input or output exception occurs

Specified by: addDateHeader in interface HttpServletResponse Parameters: name — the name of the header to set date — the additional date value See Also: HttpServletResponse.setDateHeader(java.lang.String, long)

Specified by: setHeader in interface HttpServletResponse Parameters: name — the name of the header value — the header value If it contains octet string, it should be encoded according to RFC 2047 (http://www.ietf.org/rfc/rfc2047.txt) See Also: HttpServletResponse.containsHeader(java.lang.String) , HttpServletResponse.addHeader(java.lang.String, java.lang.String)

Specified by: addHeader in interface HttpServletResponse Parameters: name — the name of the header value — the additional header value If it contains octet string, it should be encoded according to RFC 2047 (http://www.ietf.org/rfc/rfc2047.txt) See Also: HttpServletResponse.setHeader(java.lang.String, java.lang.String)

Specified by: addIntHeader in interface HttpServletResponse Parameters: name — the name of the header value — the assigned integer value See Also: HttpServletResponse.setIntHeader(java.lang.String, int)

setStatus

setStatus

The default behavior of this method is to call setStatus(int sc, String sm) on the wrapped response object.

Specified by: setStatus in interface HttpServletResponse Parameters: sc — the status code sm — the status message

getStatus

Specified by: getStatus in interface HttpServletResponse Returns: the current status code of the wrapped response

Specified by: getHeader in interface HttpServletResponse Parameters: name — the name of the response header whose value to return Returns: the value of the response header with the given name, or null if no header with the given name has been set on the wrapped response Since: Servlet 3.0

Any changes to the returned Collection must not affect this HttpServletResponseWrapper .

Specified by: getHeaders in interface HttpServletResponse Parameters: name — the name of the response header whose values to return Returns: a (possibly empty) Collection of the values of the response header with the given name Since: Servlet 3.0

Any changes to the returned Collection must not affect this HttpServletResponseWrapper .

Specified by: getHeaderNames in interface HttpServletResponse Returns: a (possibly empty) Collection of the names of the response headers Since: Servlet 3.0

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Httpservletresponse java send error

Обеспечивает удобную реализацию интерфейса HttpServletResponse, который может быть разделен на подклассы разработчиками, желающими адаптировать ответ от Сервлета. Этот class реализует Обертку или Шаблон «декоратор». Значение по умолчанию методов к вызову через к обернутому объекту ответа.

С тех пор: Сервлет 2.3 Автор: Различный См. Также: HttpServletResponse

HttpServletResponseWrapper

Броски: java.lang.IllegalArgumentException — если ответ является нулем

addCookie

Определенный: addCookie в интерфейсе HttpServletResponse Параметры: cookie — Cookie, чтобы возвратиться к клиенту

Определенный: containsHeader в интерфейсе HttpServletResponse Параметры: name — имя заголовка Возвраты: true если именованный заголовок ответа был уже установлен; false иначе

encodeURL

Определенный: encodeURL в интерфейсе HttpServletResponse Параметры: url — url, который будет закодирован. Возвраты: закодированный URL, если кодирование необходимо; неизменный URL иначе.

encodeRedirectURL

Определенный: encodeRedirectURL в интерфейсе HttpServletResponse Параметры: url — url, который будет закодирован. Возвраты: закодированный URL, если кодирование необходимо; неизменный URL иначе. См. Также: HttpServletResponse.sendRedirect(java.lang.String) , HttpServletResponse.encodeUrl(java.lang.String)

encodeUrl

Поведение значения по умолчанию этого метода должно вызвать encodeUrl (Строковый url) на обернутом объекте ответа.

Определенный: encodeUrl в интерфейсе HttpServletResponse Параметры: url — url, который будет закодирован. Возвраты: закодированный URL, если кодирование необходимо; неизменный URL иначе.

encodeRedirectUrl

Поведение значения по умолчанию этого метода должно возвратить encodeRedirectUrl (Строковый url) на обернутом объекте ответа.

Определенный: encodeRedirectUrl в интерфейсе HttpServletResponse Параметры: url — url, который будет закодирован. Возвраты: закодированный URL, если кодирование необходимо; неизменный URL иначе.

sendError

Определенный: sendError в интерфейсе HttpServletResponse Параметры: sc — код ошибки msg — дескриптивное сообщение Броски: java.io.IOException — Если исключение ввода или вывода происходит

sendError

Определенный: sendError в интерфейсе HttpServletResponse Параметры: sc — код ошибки Броски: java.io.IOException — Если исключение ввода или вывода происходит

sendRedirect

Определенный: sendRedirect в интерфейсе HttpServletResponse Параметры: location — расположение перенаправления URL Броски: java.io.IOException — Если исключение ввода или вывода происходит

Определенный: addDateHeader в интерфейсе HttpServletResponse Параметры: name — имя заголовка, чтобы установить date — дополнительное значение даты См. Также: HttpServletResponse.setDateHeader(java.lang.String, long)

Определенный: setHeader в интерфейсе HttpServletResponse Параметры: name — имя заголовка value — значение заголовка, Если это содержит строку октета, это должно быть закодировано согласно RFC 2047 (http://www.ietf.org/rfc/rfc2047.txt) См. Также: HttpServletResponse.containsHeader(java.lang.String) , HttpServletResponse.addHeader(java.lang.String, java.lang.String)

Определенный: addHeader в интерфейсе HttpServletResponse Параметры: name — имя заголовка value — дополнительный заголовок оценивает, Если он содержит строку октета, он должен быть закодирован согласно RFC 2047 (http://www.ietf.org/rfc/rfc2047.txt) См. Также: HttpServletResponse.setHeader(java.lang.String, java.lang.String)

Определенный: addIntHeader в интерфейсе HttpServletResponse Параметры: name — имя заголовка value — присвоенное целочисленное значение См. Также: HttpServletResponse.setIntHeader(java.lang.String, int)

setStatus

setStatus

Поведение значения по умолчанию этого метода должно вызвать setStatus (международный кв/см, Строковый см) на обернутом объекте ответа.

Определенный: setStatus в интерфейсе HttpServletResponse Параметры: sc — код состояния sm — сообщение о состоянии

getStatus

Определенный: getStatus в интерфейсе HttpServletResponse Возвраты: код текущего статуса обернутого ответа

Определенный: getHeader в интерфейсе HttpServletResponse Параметры: name — имя заголовка ответа, чье значение, чтобы возвратиться Возвраты: значение заголовка ответа с именем, или null, если никакой заголовок с именем не был установлен на обернутом ответе С тех пор: Сервлет 3.0

Любые изменения к возвращенному Collection не должен влиять на это HttpServletResponseWrapper .

Определенный: getHeaders в интерфейсе HttpServletResponse Параметры: name — имя заголовка ответа, чьи значения, чтобы возвратиться Возвраты: (возможно пустой) Collection из значений заголовка ответа с именем С тех пор: Сервлет 3.0

Любые изменения к возвращенному Collection не должен влиять на это HttpServletResponseWrapper .

Определенный: getHeaderNames в интерфейсе HttpServletResponse Возвраты: (возможно пустой) Collection из имен заголовков ответа С тех пор: Сервлет 3.0

Представьте ошибку или функцию

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Сгенерированный на 10-February-2011 12:41

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The HttpServletResponse interface enables a servlet to formulate an HTTP response to a client. The response object encapsulates all information to be returned from the server to the client. In the HTTP protocol, this information is transmitted from the server to the client either by HTTP headers or the message body of the request.

Check out: Servlet + JSP + JDBC + MySQL Examples

The HttpServletResponse interface extends the ServletResponse interface to provide HTTP-specific functionality in sending a response. For example, it has methods to access HTTP headers and cookies.

The servlet container creates an HttpServletResponse object and passes it as an argument to the servlet’s service methods (doGet, doPost, etc). For instance, here is the signature of the HttpServlet.doGet() method:

protected void doGet(
    HttpServletRequest request,
    HttpServletResponse response)
      throws ServletException, IOException {
}

package net.javaguides.servlet.tutorial.httpservlet;

import java.io.IOException;
import java.io.OutputStream;
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(urlPatterns = "/httpservletresponse")
public class HttpServletResponseExample extends HttpServlet {

    private static final long serialVersionUID = 1 L;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // Writing HTML
        PrintWriter printWriter = response.getWriter();

        // Headers
        response.setHeader("Header-Name", "Header Value");

        // Content-Type
        response.setContentType("text/html");

        // Content-Length
        response.setHeader("Content-Length", "31642");

        // Writing Binary Data
        OutputStream outputStream = response.getOutputStream();
        outputStream.write(123);

        //Redirecting to a Different URL
        response.sendRedirect("https://javaguides.net");

        printWriter.print("<html>");
        printWriter.print("<body>");
        printWriter.print("<h1>Hello World HttpServlet Class Example</h1>");
        printWriter.print("<a href="http://www.javaguides.net">Java Guides</a>");
        printWriter.print("</body>");
        printWriter.print("</html>");
        printWriter.close();
    }
}

The HttpServlet class request processing methods take two parameters.

1. javax.servlet.http.HttpRequest
2. javax.servlet.http.HttpResponse

The HttpServletResponse object generates a response to return to the requesting client. Its methods allow you to set the response header and the response body.

The first line of the Response header (response.setContentType(“text/html”);) identifies the MIME type of the response. The following three lines are often placed in servlet code to prevent Web browsers and proxy servers from caching dynamically-generated Web pages. If you want your dynamic Web page to be cached, remove these three lines of code.

The response object also has the getWriter() method to return a PrintWriter object. The print() and println() methods of the PrintWriter object write the servlet response back to the client.

For instance, here is the signature of the HttpServlet.doGet() method:

protected void doGet(
    HttpServletRequest request,
    HttpServletResponse response)
      throws ServletException, IOException {

}

In this text I will look at the HttpResponse object.

The purpose of the HttpResponse object is to represent the HTTP response your web application sends back to the browser, in response to the HTTP request the browser send to your web application.

Methods to Set HTTP Response Header:

There are following methods which can be used to set HTTP response header in your servlet program. These methods are available with HttpServletResponse object.

1 String encodeRedirectURL(String url)
Encodes the specified URL for use in the sendRedirect method or, if encoding is not needed, returns the URL unchanged.
2 String encodeURL(String url)
Encodes the specified URL by including the session ID in it, or, if encoding is not needed, returns the URL unchanged.
3 boolean containsHeader(String name)
Returns a boolean indicating whether the named response header has already been set.
4 boolean isCommitted()
Returns a boolean indicating if the response has been committed.
5 void addCookie(Cookie cookie)
Adds the specified cookie to the response.
6 void addDateHeader(String name, long date)
Adds a response header with the given name and date-value.
7 void addHeader(String name, String value)
Adds a response header with the given name and value.
8 void addIntHeader(String name, int value)
Adds a response header with the given name and integer value.
9 void flushBuffer()
Forces any content in the buffer to be written to the client.
10 void reset()
Clears any data that exists in the buffer as well as the status code and headers.
11 void resetBuffer()
Clears the content of the underlying buffer in the response without clearing headers or status code.
12 void sendError(int sc)
Sends an error response to the client using the specified status code and clearing the buffer.
13 void sendError(int sc, String msg)
Sends an error response to the client using the specified status.
14 void sendRedirect(String location)
Sends a temporary redirect response to the client using the specified redirect location URL.
15 void setBufferSize(int size)
Sets the preferred buffer size for the body of the response.
16 void setCharacterEncoding(String charset)
Sets the character encoding (MIME charset) of the response being sent to the client, for example, to UTF-8.
17 void setContentLength(int len)
Sets the length of the content body in the response In HTTP servlets, this method sets the HTTP Content-Length header.
18 void setContentType(String type)
Sets the content type of the response being sent to the client, if the response has not been committed yet.
19 void setDateHeader(String name, long date)
Sets a response header with the given name and date-value.
20 void setHeader(String name, String value)
Sets a response header with the given name and value.
21 void setIntHeader(String name, int value)
Sets a response header with the given name and integer value.
22 void setLocale(Locale loc)
Sets the locale of the response, if the response has not been committed yet.
23 void setStatus(int sc)
Sets the status code for this response.

The HttpResponse object has a lot of methods, so I will just cover the most commonly used here. The rest you can read about in the JavaDoc, if you are interested. The parts I will cover are:

1. Writing HTML
2. Headers
3. Content-Type
4. Writing Text
5. Content-Length
6. Writing Binary Data
7. Redirecting to a Different URL
8. Writing HTML

To send HTML back to the browser, you have to obtain the a PrintWriter from the HttpResponse object. Here is how:

PrintWriter writer = response.getWriter();

writer.write("<html><body>GET/POST response</body></html>");

Headers

Just like the request object, the HttpRequest can contain HTTP headers. Headers must be set before any data is written to the response. You set a header on the response object like this:

response.setHeader("Header-Name", "Header Value");

As you can see, a response header is a name, value pair.

Content-Type

The Content-Type header is a response header that tells the browser the type of the content you are sending back to it. For instance, the content type for HTML is text/html. Similarly, if what you send back to the browser is plain text, you use the content type text/plain.

Here is how you set the Content-Type header on the HttpResponse object:

response.setHeader("Content-Type", "text/html");

Writing Text

You can write text back to the browser instead of HTML, like this:

response.setHeader("Content-Type", "text/plain");

PrintWriter writer = response.getWriter();
writer.write("This is just plain text");

First the Content-Type header is set to text/plain. Then a plain text string is written to the writer obtained from the response object.

Content-Length

The Content-Length header tells the browser how many bytes your servlet is sending back. If you are sending binary data back you need to set the content length header. Here is how:

response.setHeader("Content-Length", "31642");

Writing Binary Data

You can also write binary data back to the browser instead of text. For instance, you can send an image back, a PDF file or a Flash file or something like that.

Again, you will first have to set the Content-Type header to the type matching the data you are sending back. For instance, the content type for a PNG image is image/png.

You can search for “mime types” in your favourite search engine to find a list of mime types (content types), so you can find the mime type for the content you are sending back.

In order to write binary data back to the browser you cannot use the Writer obtained from response.getWriter(). Afterall, Writer’s are intended for text.

Instead you have to use the OutputStream obtained from the response.getOutputStream() method. Here is how:

OutputStream outputStream = response.getOutputStream();
outputStream.write(...);

Redirecting to a Different URL

You can redirect the browser to a different URL from your servlet. You cannot send any data back to the browser when redirecting. Here is how you redirect:

response.sendRedirect("https://www.dineshonjava.com");

Create the HTTP response

After the servlet request code, add the response code:

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class ServletSample extends HttpServlet
{

   public void doGet (HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException
   {

      Enumeration keys;
      String key;
      String myName = "";
      keys = request.getParameterNames();
      while (keys.hasMoreElements())
      {
         key = (String) keys.nextElement();
         if (key.equalsIgnoreCase("myName")) myName = request.getParameter(key);
      }
      System.out.println("Name = ");
      if (myName == "") myName = "Hello";

      response.setContentType("text/html"); 
      response.setHeader("Pragma", "No-cache");
      response.setDateHeader("Expires", 0);
      response.setHeader("Cache-Control", "no-cache");
   
      PrintWriter out = response.getWriter(); 
      out.println("<html>");  
      out.println("<head><title>Just a basic servlet</title></head>");
      out.println("<body>");
      out.println("<h1>Just a basic servlet</h1>");
      out.println ("<p>" + myName +  ", this is a very basic servlet.");
      out.println("</body></html>");    
      out.flush();

   }
}

As discussed in the previous chapter, when a Web server responds to an HTTP request, the response typically consists of a status line, some response headers, a blank line, and the document. A typical response looks like this −

HTTP/1.1 200 OK
Content-Type: text/html
Header2: ...
...
HeaderN: ...
   (Blank Line)
<!doctype ...>
<html>
   <head>...</head>
   <body>
      ...
   </body>
</html>

The status line consists of the HTTP version (HTTP/1.1 in the example), a status code (200 in the example), and a very short message corresponding to the status code (OK in the example).

Following is a summary of the most useful HTTP 1.1 response headers which go back to the browser from web server side and you would use them very frequently in web programming −

Methods to Set HTTP Response Header

There are following methods which can be used to set HTTP response header in your servlet program. These methods are available with HttpServletResponse object.

HTTP Header Response Example

You already have seen setContentType() method working in previous examples and following example would also use same method, additionally we would use setIntHeader() method to set Refresh header.

// Import required java libraries
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
 
// Extend HttpServlet class
public class Refresh extends HttpServlet {
 
   // Method to handle GET method request.
   public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
   
      // Set refresh, autoload time as 5 seconds
      response.setIntHeader("Refresh", 5);
 
      // Set response content type
      response.setContentType("text/html");
 
      // Get current time
      Calendar calendar = new GregorianCalendar();
      String am_pm;
      int hour = calendar.get(Calendar.HOUR);
      int minute = calendar.get(Calendar.MINUTE);
      int second = calendar.get(Calendar.SECOND);
         
      if(calendar.get(Calendar.AM_PM) == 0)
         am_pm = "AM";
      else
         am_pm = "PM";
 
      String CT = hour+":"+ minute +":"+ second +" "+ am_pm;
    
      PrintWriter out = response.getWriter();
      String title = "Auto Refresh Header Setting";
      String docType =
         "<!doctype html public "-//w3c//dtd html 4.0 " + "transitional//en">n";

      out.println(docType +
         "<html>n" +
         "<head><title>" + title + "</title></head>n"+
         "<body bgcolor = "#f0f0f0">n" +
         "<h1 align = "center">" + title + "</h1>n" +
         "<p>Current Time is: " + CT + "</p>n"
      );
   }
   
   // Method to handle POST method request.
   public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
      
      doGet(request, response);
   }
}

Now calling the above servlet would display current system time after every 5 seconds as follows. Just run the servlet and wait to see the result −

Auto Refresh Header Setting
Current Time is: 9:44:50 PM