[英]Checking Content-Type of HTTP POST Request to Java servlet
I've written a simple servlet that accepts HTTP POST requests and sends back a short response. 我编写了一个简单的servlet,它接受HTTP POST请求并发回一个简短的响应。 Here's the code for the servlet:
这是servlet的代码:
import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.*;
/**
* Servlet implementation class MapleTAServlet
*/
@WebServlet(description = "Receives XML request text containing grade data and returns response in XML", urlPatterns = { "/MapleTAServlet" })
public class MapleTAServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private Log log = LogFactory.getLog(MapleTAServlet.class);
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
String strXMLResponse = "<Response><code>";
String strMessage = "";
int intCode = 0;
ServletOutputStream stream = null;
BufferedInputStream buffer = null;
try
{
String strContentType = request.getContentType();
// Make sure that the incoming request is XML data, otherwise throw up a red flag
if (strContentType != "text/xml")
{
strMessage = "Incorrect MIME type";
}
else
{
intCode = 1;
} // end if
strXMLResponse += intCode + "</code><message>" + strMessage + "</message></Response>";
response.setContentType("text/xml");
response.setContentLength(strXMLResponse.length());
int intReadBytes = 0;
stream = response.getOutputStream();
// Converts the XML string to an input stream of a byte array
ByteArrayInputStream bs = new ByteArrayInputStream(strXMLResponse.getBytes());
buffer = new BufferedInputStream(bs);
while ((intReadBytes = buffer.read()) != -1)
{
stream.write(intReadBytes);
} // end while
}
catch (IOException e)
{
log.error(e.getMessage());
}
catch (Exception e)
{
log.error(e.getMessage());
}
finally
{
stream.close();
buffer.close();
} // end try-catch
}
}
And here's the client that I'm using to send the request: 这是我用来发送请求的客户端:
import java.net.HttpURLConnection;
import java.net.URL;
import java.io.*;
public class TestClient
{
/**
* @param args
*/
public static void main(String[] args)
{
BufferedReader inStream = null;
try
{
// Connect to servlet
URL url = new URL("http://localhost/mapleta/mtaservlet");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
// Initialize the connection
conn.setDoOutput(true);
conn.setDoInput(true);
conn.setRequestMethod("POST");
conn.setUseCaches(false);
conn.setRequestProperty("Content-Type", "text/xml");
//conn.setRequestProperty("Connection", "Keep-Alive");
conn.connect();
OutputStream out = conn.getOutputStream();
inStream = new BufferedReader(new InputStreamReader(conn.getInputStream()));
String strXMLRequest = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><Request></Request>";
out.write(strXMLRequest.getBytes());
out.flush();
out.close();
String strServerResponse = "";
System.out.println("Server says: ");
while ((strServerResponse = inStream.readLine()) != null)
{
System.out.println(strServerResponse);
} // end while
inStream.close();
}
catch (IOException e)
{
e.printStackTrace();
}
catch (Exception e)
{
e.printStackTrace();
} // end try catch
}
}
The issue I'm having is that when I run the client program, I'm getting the following output: 我遇到的问题是,当我运行客户端程序时,我得到以下输出:
Server says:
<Response><code>0</code><message>Incorrect MIME type</message></Response>
I've tried calling request.getContentType() and have gotten "text/xml" as the output. 我试过调用request.getContentType()并得到“text / xml”作为输出。 Just trying to figure out why the string isn't matching up.
只是想弄清楚为什么字符串不匹配。
You're comparing strings the wrong way. 你用错误的方式比较字符串。
if (strContentType != "text/xml")
Strings are not primitives , they are objects . 字符串不是原始字母 ,它们是对象 。 When using
!=
to compare two objects, it will only test if they do not point to the same reference . 当使用
!=
来比较两个对象时,它只会测试它们是否指向相同的引用 。 However, you're rather interested in comparing the content of two different string references, not if they point to the same reference. 但是,您对比较两个不同字符串引用的内容非常感兴趣,而不是它们指向相同的引用。
You should then use the equals()
method for this: 然后,您应该使用
equals()
方法 :
if (!strContentType.equals("text/xml"))
Or, better, to avoid NullPointerException
if the Content-Type
header is not present (and thus becomes null
): 或者,更好的是,如果
Content-Type
标头不存在(因此变为null
), NullPointerException
避免NullPointerException
:
if (!"text/xml".equals(strContentType))
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