Java Tutorial/Servlet/Request
Содержание
Get Remote Host from Servlet Request
<source lang="java">
import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class MyServlet extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/html");
PrintWriter out = res.getWriter();
// Get the client"s hostname
String remoteHost = req.getRemoteHost();
out.println("remoteHost:"+remoteHost);
// See if the client is allowed
if (! isHostAllowed(remoteHost)) {
out.println("Access <BLINK>denied</BLINK>");
}
else {
out.println("Access granted");
// Display download links, etc...
}
}
// Disallow hosts ending with .cu, .ir, .iq, .kp, .ly, .sy, and .sd.
private boolean isHostAllowed(String host) {
return (!host.endsWith(".cu") &&
!host.endsWith(".ir") &&
!host.endsWith(".iq") &&
!host.endsWith(".kp") &&
!host.endsWith(".ly") &&
!host.endsWith(".sy") &&
!host.endsWith(".sd"));
}
}</source>
Get Remote User and display welcome message
<source lang="java">
import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.util.*; public class MyServlet extends HttpServlet {
Hashtable accesses = new Hashtable();
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/html");
PrintWriter out = res.getWriter();
String remoteUser = req.getRemoteUser();
if (remoteUser == null) {
out.println("Welcome!");
}
else {
out.println("Welcome, " + remoteUser + "!");
Date lastAccess = (Date) accesses.get(remoteUser);
if (lastAccess == null) {
out.println("This is your first visit!");
}
else {
out.println("Your last visit was " + accesses.get(remoteUser));
}
if (remoteUser.equals("YourFirendName")) {
out.println("Shall we play a game?");
}
accesses.put(remoteUser, new Date());
}
}
}</source>
Get Servlet Request Parameter
<source lang="java">
import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.util.*; import java.text.DateFormat; public class MyServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
ServletOutputStream out = response.getOutputStream();
String fileName = request.getParameter("file");
out.println("<html>");
out.println("<head>");
out.println("<title>Welcome</title>");
out.println("</head>");
out.println("<body>");
out.println("The File
"); out.println(fileName);
out.println("</body>");
out.println("</html>");
out.close();
} //end doGet
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request,response);
}
}</source>
Get Users IP Address
<source lang="java">
import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class Main extends HttpServlet {
protected void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
// Print out the IP address of the caller
out.println(request.getRemoteAddr());
}
}</source>
Print Request Headers for a Servlet
<source lang="java">
import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.util.*; public class MyServlet extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/plain");
PrintWriter out = res.getWriter();
out.println("Request Headers:");
out.println();
Enumeration names = req.getHeaderNames();
while (names.hasMoreElements()) {
String name = (String) names.nextElement();
Enumeration values = req.getHeaders(name); // support multiple values
if (values != null) {
while (values.hasMoreElements()) {
String value = (String) values.nextElement();
out.println(name + ": " + value);
}
}
}
}
}</source>
Request parsing and encoding utility methods
<source lang="java">
/*
* Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */
import java.io.UnsupportedEncodingException; import java.text.SimpleDateFormat; import java.util.Map; import java.util.TimeZone;
/**
* General purpose request parsing and encoding utility methods. * * @author Craig R. McClanahan * @author Tim Tye * @version $Revision: 901 $ $Date: 2009-01-15 16:49:36 +0100 (Thu, 15 Jan 2009) $ */
public final class RequestUtil {
/**
* The DateFormat to use for generating readable dates in cookies.
*/
private static SimpleDateFormat format =
new SimpleDateFormat(" EEEE, dd-MMM-yy kk:mm:ss zz");
static {
format.setTimeZone(TimeZone.getTimeZone("GMT"));
}
/**
* Filter the specified message string for characters that are sensitive
* in HTML. This avoids potential attacks caused by including JavaScript
* codes in the request URL that is often reported in error messages.
*
* @param message The message string to be filtered
*/
public static String filter(String message) {
if (message == null)
return (null);
char content[] = new char[message.length()];
message.getChars(0, message.length(), content, 0);
StringBuffer result = new StringBuffer(content.length + 50);
for (int i = 0; i < content.length; i++) {
switch (content[i]) {
case "<":
result.append("<");
break;
case ">":
result.append(">");
break;
case "&":
result.append("&");
break;
case """:
result.append(""");
break;
default:
result.append(content[i]);
}
}
return (result.toString());
}
/**
* Normalize a relative URI path that may have relative values ("/./",
* "/../", and so on ) it it. WARNING - This method is
* useful only for normalizing application-generated paths. It does not
* try to perform security checks for malicious input.
*
* @param path Relative path to be normalized
*/
public static String normalize(String path) {
return normalize(path, true);
}
/**
* Normalize a relative URI path that may have relative values ("/./",
* "/../", and so on ) it it. WARNING - This method is
* useful only for normalizing application-generated paths. It does not
* try to perform security checks for malicious input.
*
* @param path Relative path to be normalized
* @param replaceBackSlash Should "\\" be replaced with "/"
*/
public static String normalize(String path, boolean replaceBackSlash) {
if (path == null)
return null;
// Create a place for the normalized path
String normalized = path;
if (replaceBackSlash && normalized.indexOf("\\") >= 0)
normalized = normalized.replace("\\", "/");
if (normalized.equals("/."))
return "/";
// Add a leading "/" if necessary
if (!normalized.startsWith("/"))
normalized = "/" + normalized;
// Resolve occurrences of "//" in the normalized path
while (true) {
int index = normalized.indexOf("//");
if (index < 0)
break;
normalized = normalized.substring(0, index) +
normalized.substring(index + 1);
}
// Resolve occurrences of "/./" in the normalized path
while (true) {
int index = normalized.indexOf("/./");
if (index < 0)
break;
normalized = normalized.substring(0, index) +
normalized.substring(index + 2);
}
// Resolve occurrences of "/../" in the normalized path
while (true) {
int index = normalized.indexOf("/../");
if (index < 0)
break;
if (index == 0)
return (null); // Trying to go outside our context
int index2 = normalized.lastIndexOf("/", index - 1);
normalized = normalized.substring(0, index2) +
normalized.substring(index + 3);
}
// Return the normalized path that we have completed
return (normalized);
}
/**
* Append request parameters from the specified String to the specified
* Map. It is presumed that the specified Map is not accessed from any
* other thread, so no synchronization is performed.
* * IMPLEMENTATION NOTE: URL decoding is performed * individually on the parsed name and value elements, rather than on * the entire query string ahead of time, to properly deal with the case * where the name or value includes an encoded "=" or "&" character * that would otherwise be interpreted as a delimiter. * * @param map Map that accumulates the resulting parameters * @param data Input string containing request parameters * * @exception IllegalArgumentException if the data is malformed */ public static void parseParameters(Map map, String data, String encoding) throws UnsupportedEncodingException { if ((data != null) && (data.length() > 0)) { // use the specified encoding to extract bytes out of the // given string so that the encoding is not lost. If an // encoding is not specified, let it use platform default byte[] bytes = null; try { if (encoding == null) { bytes = data.getBytes(); } else { bytes = data.getBytes(encoding); } } catch (UnsupportedEncodingException uee) { } parseParameters(map, bytes, encoding); } } /** * Decode and return the specified URL-encoded String. * When the byte array is converted to a string, the system default * character encoding is used... This may be different than some other * servers. It is assumed the string is not a query string. * * @param str The url-encoded string * * @exception IllegalArgumentException if a "%" character is not followed * by a valid 2-digit hexadecimal number */ public static String URLDecode(String str) { return URLDecode(str, null); } /** * Decode and return the specified URL-encoded String. It is assumed the * string is not a query string. * * @param str The url-encoded string * @param enc The encoding to use; if null, the default encoding is used * @exception IllegalArgumentException if a "%" character is not followed * by a valid 2-digit hexadecimal number */ public static String URLDecode(String str, String enc) { return URLDecode(str, enc, false); } /** * Decode and return the specified URL-encoded String. * * @param str The url-encoded string * @param enc The encoding to use; if null, the default encoding is used * @param isQuery Is this a query string being processed * @exception IllegalArgumentException if a "%" character is not followed * by a valid 2-digit hexadecimal number */ public static String URLDecode(String str, String enc, boolean isQuery) { if (str == null) return (null); // use the specified encoding to extract bytes out of the // given string so that the encoding is not lost. If an // encoding is not specified, let it use platform default byte[] bytes = null; try { if (enc == null) { bytes = str.getBytes(); } else { bytes = str.getBytes(enc); } } catch (UnsupportedEncodingException uee) {} return URLDecode(bytes, enc, isQuery); } /** * Decode and return the specified URL-encoded byte array. * * @param bytes The url-encoded byte array * @exception IllegalArgumentException if a "%" character is not followed * by a valid 2-digit hexadecimal number */ public static String URLDecode(byte[] bytes) { return URLDecode(bytes, null); } /** * Decode and return the specified URL-encoded byte array. * * @param bytes The url-encoded byte array * @param enc The encoding to use; if null, the default encoding is used * @exception IllegalArgumentException if a "%" character is not followed * by a valid 2-digit hexadecimal number */ public static String URLDecode(byte[] bytes, String enc) { return URLDecode(bytes, null, false); } /** * Decode and return the specified URL-encoded byte array. * * @param bytes The url-encoded byte array * @param enc The encoding to use; if null, the default encoding is used * @param isQuery Is this a query string being processed * @exception IllegalArgumentException if a "%" character is not followed * by a valid 2-digit hexadecimal number */ public static String URLDecode(byte[] bytes, String enc, boolean isQuery) { if (bytes == null) return (null); int len = bytes.length; int ix = 0; int ox = 0; while (ix < len) { byte b = bytes[ix++]; // Get byte to test if (b == "+" && isQuery) { b = (byte)" "; } else if (b == "%") { b = (byte) ((convertHexDigit(bytes[ix++]) << 4) + convertHexDigit(bytes[ix++])); } bytes[ox++] = b; } if (enc != null) { try { return new String(bytes, 0, ox, enc); } catch (Exception e) { e.printStackTrace(); } } return new String(bytes, 0, ox); } /** * Convert a byte character value to hexidecimal digit value. * * @param b the character value byte */ private static byte convertHexDigit( byte b ) { if ((b >= "0") && (b <= "9")) return (byte)(b - "0"); if ((b >= "a") && (b <= "f")) return (byte)(b - "a" + 10); if ((b >= "A") && (b <= "F")) return (byte)(b - "A" + 10); return 0; } /** * Put name and value pair in map. When name already exist, add value * to array of values. * * @param map The map to populate * @param name The parameter name * @param value The parameter value */ private static void putMapEntry( Map map, String name, String value) { String[] newValues = null; String[] oldValues = (String[]) map.get(name); if (oldValues == null) { newValues = new String[1]; newValues[0] = value; } else { newValues = new String[oldValues.length + 1]; System.arraycopy(oldValues, 0, newValues, 0, oldValues.length); newValues[oldValues.length] = value; } map.put(name, newValues); } /** * Append request parameters from the specified String to the specified * Map. It is presumed that the specified Map is not accessed from any * other thread, so no synchronization is performed. * <p> * IMPLEMENTATION NOTE: URL decoding is performed * individually on the parsed name and value elements, rather than on * the entire query string ahead of time, to properly deal with the case * where the name or value includes an encoded "=" or "&" character * that would otherwise be interpreted as a delimiter. * * NOTE: byte array data is modified by this method. Caller beware. * * @param map Map that accumulates the resulting parameters * @param data Input string containing request parameters * @param encoding Encoding to use for converting hex * * @exception UnsupportedEncodingException if the data is malformed */ public static void parseParameters(Map map, byte[] data, String encoding) throws UnsupportedEncodingException { if (data != null && data.length > 0) { int ix = 0; int ox = 0; String key = null; String value = null; while (ix < data.length) { byte c = data[ix++]; switch ((char) c) { case "&": value = new String(data, 0, ox, encoding); if (key != null) { putMapEntry(map, key, value); key = null; } ox = 0; break; case "=": if (key == null) { key = new String(data, 0, ox, encoding); ox = 0; } else { data[ox++] = c; } break; case "+": data[ox++] = (byte)" "; break; case "%": data[ox++] = (byte)((convertHexDigit(data[ix++]) << 4) + convertHexDigit(data[ix++])); break; default: data[ox++] = c; } } //The last value does not end in "&". So save it now. if (key != null) { value = new String(data, 0, ox, encoding); putMapEntry(map, key, value); } } } }</source>
