/**
* 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.
*/
package org.apache.hadoop.hdfs.server.common;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.URL;
import java.net.URLEncoder;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.TreeSet;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspWriter;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hdfs.BlockReader;
import org.apache.hadoop.hdfs.BlockReaderFactory;
import org.apache.hadoop.hdfs.DFSConfigKeys;
import org.apache.hadoop.hdfs.DFSUtil;
import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
import org.apache.hadoop.hdfs.protocol.LocatedBlock;
import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenIdentifier;
import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor;
import org.apache.hadoop.hdfs.server.namenode.NameNode;
import org.apache.hadoop.hdfs.server.namenode.NameNodeHttpServer;
import org.apache.hadoop.hdfs.web.resources.DelegationParam;
import org.apache.hadoop.hdfs.web.resources.DoAsParam;
import org.apache.hadoop.hdfs.web.resources.UserParam;
import org.apache.hadoop.http.HtmlQuoting;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.net.NetUtils;
import org.apache.hadoop.security.AccessControlException;
import org.apache.hadoop.security.SecurityUtil;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.UserGroupInformation.AuthenticationMethod;
import org.apache.hadoop.security.authentication.util.KerberosName;
import org.apache.hadoop.security.authorize.AuthorizationException;
import org.apache.hadoop.security.authorize.ProxyUsers;
import org.apache.hadoop.security.token.Token;
import org.apache.hadoop.util.VersionInfo;
@InterfaceAudience.Private
public class JspHelper {
public static final String CURRENT_CONF = "current.conf";
final static public String WEB_UGI_PROPERTY_NAME = DFSConfigKeys.DFS_WEB_UGI_KEY;
public static final String DELEGATION_PARAMETER_NAME = DelegationParam.NAME;
public static final String NAMENODE_ADDRESS = "nnaddr";
static final String SET_DELEGATION = "&" + DELEGATION_PARAMETER_NAME +
"=";
private static final Log LOG = LogFactory.getLog(JspHelper.class);
/** Private constructor for preventing creating JspHelper object. */
private JspHelper() {}
// data structure to count number of blocks on datanodes.
private static class NodeRecord extends DatanodeInfo {
int frequency;
public NodeRecord() {
frequency = -1;
}
public NodeRecord(DatanodeInfo info, int count) {
super(info);
this.frequency = count;
}
@Override
public boolean equals(Object obj) {
// Sufficient to use super equality as datanodes are uniquely identified
// by DatanodeID
return (this == obj) || super.equals(obj);
}
@Override
public int hashCode() {
// Super implementation is sufficient
return super.hashCode();
}
}
// compare two records based on their frequency
private static class NodeRecordComparator implements Comparator<NodeRecord> {
public int compare(NodeRecord o1, NodeRecord o2) {
if (o1.frequency < o2.frequency) {
return -1;
} else if (o1.frequency > o2.frequency) {
return 1;
}
return 0;
}
}
public static DatanodeInfo bestNode(LocatedBlocks blks, Configuration conf)
throws IOException {
HashMap<DatanodeInfo, NodeRecord> map =
new HashMap<DatanodeInfo, NodeRecord>();
for (LocatedBlock block : blks.getLocatedBlocks()) {
DatanodeInfo[] nodes = block.getLocations();
for (DatanodeInfo node : nodes) {
NodeRecord record = map.get(node);
if (record == null) {
map.put(node, new NodeRecord(node, 1));
} else {
record.frequency++;
}
}
}
NodeRecord[] nodes = map.values().toArray(new NodeRecord[map.size()]);
Arrays.sort(nodes, new NodeRecordComparator());
return bestNode(nodes, false, conf);
}
public static DatanodeInfo bestNode(LocatedBlock blk, Configuration conf)
throws IOException {
DatanodeInfo[] nodes = blk.getLocations();
return bestNode(nodes, true, conf);
}
public static DatanodeInfo bestNode(DatanodeInfo[] nodes, boolean doRandom,
Configuration conf) throws IOException {
TreeSet<DatanodeInfo> deadNodes = new TreeSet<DatanodeInfo>();
DatanodeInfo chosenNode = null;
int failures = 0;
Socket s = null;
int index = -1;
if (nodes == null || nodes.length == 0) {
throw new IOException("No nodes contain this block");
}
while (s == null) {
if (chosenNode == null) {
do {
if (doRandom) {
index = DFSUtil.getRandom().nextInt(nodes.length);
} else {
index++;
}
chosenNode = nodes[index];
} while (deadNodes.contains(chosenNode));
}
chosenNode = nodes[index];
//just ping to check whether the node is alive
InetSocketAddress targetAddr = NetUtils.createSocketAddr(
chosenNode.getHost() + ":" + chosenNode.getInfoPort());
try {
s = NetUtils.getDefaultSocketFactory(conf).createSocket();
s.connect(targetAddr, HdfsServerConstants.READ_TIMEOUT);
s.setSoTimeout(HdfsServerConstants.READ_TIMEOUT);
} catch (IOException e) {
deadNodes.add(chosenNode);
s.close();
s = null;
failures++;
}
if (failures == nodes.length)
throw new IOException("Could not reach the block containing the data. Please try again");
}
s.close();
return chosenNode;
}
public static void streamBlockInAscii(InetSocketAddress addr, String poolId,
long blockId, Token<BlockTokenIdentifier> blockToken, long genStamp,
long blockSize, long offsetIntoBlock, long chunkSizeToView,
JspWriter out, Configuration conf) throws IOException {
if (chunkSizeToView == 0) return;
Socket s = NetUtils.getDefaultSocketFactory(conf).createSocket();
s.connect(addr, HdfsServerConstants.READ_TIMEOUT);
s.setSoTimeout(HdfsServerConstants.READ_TIMEOUT);
int amtToRead = (int)Math.min(chunkSizeToView, blockSize - offsetIntoBlock);
// Use the block name for file name.
String file = BlockReaderFactory.getFileName(addr, poolId, blockId);
BlockReader blockReader = BlockReaderFactory.newBlockReader(
conf, s, file,
new ExtendedBlock(poolId, blockId, 0, genStamp), blockToken,
offsetIntoBlock, amtToRead);
byte[] buf = new byte[(int)amtToRead];
int readOffset = 0;
int retries = 2;
while ( amtToRead > 0 ) {
int numRead = amtToRead;
try {
blockReader.readFully(buf, readOffset, amtToRead);
}
catch (IOException e) {
retries--;
if (retries == 0)
throw new IOException("Could not read data from datanode");
continue;
}
amtToRead -= numRead;
readOffset += numRead;
}
blockReader = null;
s.close();
out.print(HtmlQuoting.quoteHtmlChars(new String(buf)));
}
public static void addTableHeader(JspWriter out) throws IOException {
out.print("<table border=\"1\""+
" cellpadding=\"2\" cellspacing=\"2\">");
out.print("<tbody>");
}
public static void addTableRow(JspWriter out, String[] columns) throws IOException {
out.print("<tr>");
for (int i = 0; i < columns.length; i++) {
out.print("<td style=\"vertical-align: top;\"><B>"+columns[i]+"</B><br></td>");
}
out.print("</tr>");
}
public static void addTableRow(JspWriter out, String[] columns, int row) throws IOException {
out.print("<tr>");
for (int i = 0; i < columns.length; i++) {
if (row/2*2 == row) {//even
out.print("<td style=\"vertical-align: top;background-color:LightGrey;\"><B>"+columns[i]+"</B><br></td>");
} else {
out.print("<td style=\"vertical-align: top;background-color:LightBlue;\"><B>"+columns[i]+"</B><br></td>");
}
}
out.print("</tr>");
}
public static void addTableFooter(JspWriter out) throws IOException {
out.print("</tbody></table>");
}
public static void sortNodeList(final List<DatanodeDescriptor> nodes,
String field, String order) {
class NodeComapare implements Comparator<DatanodeDescriptor> {
static final int
FIELD_NAME = 1,
FIELD_LAST_CONTACT = 2,
FIELD_BLOCKS = 3,
FIELD_CAPACITY = 4,
FIELD_USED = 5,
FIELD_PERCENT_USED = 6,
FIELD_NONDFS_USED = 7,
FIELD_REMAINING = 8,
FIELD_PERCENT_REMAINING = 9,
FIELD_ADMIN_STATE = 10,
FIELD_DECOMMISSIONED = 11,
SORT_ORDER_ASC = 1,
SORT_ORDER_DSC = 2;
int sortField = FIELD_NAME;
int sortOrder = SORT_ORDER_ASC;
public NodeComapare(String field, String order) {
if (field.equals("lastcontact")) {
sortField = FIELD_LAST_CONTACT;
} else if (field.equals("capacity")) {
sortField = FIELD_CAPACITY;
} else if (field.equals("used")) {
sortField = FIELD_USED;
} else if (field.equals("nondfsused")) {
sortField = FIELD_NONDFS_USED;
} else if (field.equals("remaining")) {
sortField = FIELD_REMAINING;
} else if (field.equals("pcused")) {
sortField = FIELD_PERCENT_USED;
} else if (field.equals("pcremaining")) {
sortField = FIELD_PERCENT_REMAINING;
} else if (field.equals("blocks")) {
sortField = FIELD_BLOCKS;
} else if (field.equals("adminstate")) {
sortField = FIELD_ADMIN_STATE;
} else if (field.equals("decommissioned")) {
sortField = FIELD_DECOMMISSIONED;
} else {
sortField = FIELD_NAME;
}
if (order.equals("DSC")) {
sortOrder = SORT_ORDER_DSC;
} else {
sortOrder = SORT_ORDER_ASC;
}
}
public int compare(DatanodeDescriptor d1,
DatanodeDescriptor d2) {
int ret = 0;
switch (sortField) {
case FIELD_LAST_CONTACT:
ret = (int) (d2.getLastUpdate() - d1.getLastUpdate());
break;
case FIELD_CAPACITY:
long dlong = d1.getCapacity() - d2.getCapacity();
ret = (dlong < 0) ? -1 : ((dlong > 0) ? 1 : 0);
break;
case FIELD_USED:
dlong = d1.getDfsUsed() - d2.getDfsUsed();
ret = (dlong < 0) ? -1 : ((dlong > 0) ? 1 : 0);
break;
case FIELD_NONDFS_USED:
dlong = d1.getNonDfsUsed() - d2.getNonDfsUsed();
ret = (dlong < 0) ? -1 : ((dlong > 0) ? 1 : 0);
break;
case FIELD_REMAINING:
dlong = d1.getRemaining() - d2.getRemaining();
ret = (dlong < 0) ? -1 : ((dlong > 0) ? 1 : 0);
break;
case FIELD_PERCENT_USED:
double ddbl =((d1.getDfsUsedPercent())-
(d2.getDfsUsedPercent()));
ret = (ddbl < 0) ? -1 : ((ddbl > 0) ? 1 : 0);
break;
case FIELD_PERCENT_REMAINING:
ddbl =((d1.getRemainingPercent())-
(d2.getRemainingPercent()));
ret = (ddbl < 0) ? -1 : ((ddbl > 0) ? 1 : 0);
break;
case FIELD_BLOCKS:
ret = d1.numBlocks() - d2.numBlocks();
break;
case FIELD_ADMIN_STATE:
ret = d1.getAdminState().toString().compareTo(
d2.getAdminState().toString());
break;
case FIELD_DECOMMISSIONED:
ret = DFSUtil.DECOM_COMPARATOR.compare(d1, d2);
break;
case FIELD_NAME:
ret = d1.getHostName().compareTo(d2.getHostName());
break;
}
return (sortOrder == SORT_ORDER_DSC) ? -ret : ret;
}
}
Collections.sort(nodes, new NodeComapare(field, order));
}
public static void printPathWithLinks(String dir, JspWriter out,
int namenodeInfoPort,
String tokenString,
String nnAddress
) throws IOException {
try {
String[] parts = dir.split(Path.SEPARATOR);
StringBuilder tempPath = new StringBuilder(dir.length());
out.print("<a href=\"browseDirectory.jsp" + "?dir="+ Path.SEPARATOR
+ "&namenodeInfoPort=" + namenodeInfoPort
+ getDelegationTokenUrlParam(tokenString)
+ getUrlParam(NAMENODE_ADDRESS, nnAddress) + "\">" + Path.SEPARATOR
+ "</a>");
tempPath.append(Path.SEPARATOR);
for (int i = 0; i < parts.length-1; i++) {
if (!parts[i].equals("")) {
tempPath.append(parts[i]);
out.print("<a href=\"browseDirectory.jsp" + "?dir="
+ tempPath.toString() + "&namenodeInfoPort=" + namenodeInfoPort
+ getDelegationTokenUrlParam(tokenString)
+ getUrlParam(NAMENODE_ADDRESS, nnAddress));
out.print("\">" + parts[i] + "</a>" + Path.SEPARATOR);
tempPath.append(Path.SEPARATOR);
}
}
if(parts.length > 0) {
out.print(parts[parts.length-1]);
}
}
catch (UnsupportedEncodingException ex) {
ex.printStackTrace();
}
}
public static void printGotoForm(JspWriter out,
int namenodeInfoPort,
String tokenString,
String file,
String nnAddress) throws IOException {
out.print("<form action=\"browseDirectory.jsp\" method=\"get\" name=\"goto\">");
out.print("Goto : ");
out.print("<input name=\"dir\" type=\"text\" width=\"50\" id\"dir\" value=\""+ file+"\">");
out.print("<input name=\"go\" type=\"submit\" value=\"go\">");
out.print("<input name=\"namenodeInfoPort\" type=\"hidden\" "
+ "value=\"" + namenodeInfoPort + "\">");
if (UserGroupInformation.isSecurityEnabled()) {
out.print("<input name=\"" + DELEGATION_PARAMETER_NAME
+ "\" type=\"hidden\" value=\"" + tokenString + "\">");
}
out.print("<input name=\""+ NAMENODE_ADDRESS +"\" type=\"hidden\" "
+ "value=\"" + nnAddress + "\">");
out.print("</form>");
}
public static void createTitle(JspWriter out,
HttpServletRequest req,
String file) throws IOException{
if(file == null) file = "";
int start = Math.max(0,file.length() - 100);
if(start != 0)
file = "..." + file.substring(start, file.length());
out.print("<title>HDFS:" + file + "</title>");
}
/** Convert a String to chunk-size-to-view. */
public static int string2ChunkSizeToView(String s, int defaultValue) {
int n = s == null? 0: Integer.parseInt(s);
return n > 0? n: defaultValue;
}
/** Return a table containing version information. */
public static String getVersionTable() {
return "<div id='dfstable'><table>"
+ "\n <tr><td id='col1'>Version:</td><td>" + VersionInfo.getVersion() + ", " + VersionInfo.getRevision()
+ "\n <tr><td id='col1'>Compiled:</td><td>" + VersionInfo.getDate() + " by " + VersionInfo.getUser() + " from " + VersionInfo.getBranch()
+ "\n</table></div>";
}
/**
* Validate filename.
* @return null if the filename is invalid.
* Otherwise, return the validated filename.
*/
public static String validatePath(String p) {
return p == null || p.length() == 0?
null: new Path(p).toUri().getPath();
}
/**
* Validate a long value.
* @return null if the value is invalid.
* Otherwise, return the validated Long object.
*/
public static Long validateLong(String value) {
return value == null? null: Long.parseLong(value);
}
/**
* Validate a URL.
* @return null if the value is invalid.
* Otherwise, return the validated URL String.
*/
public static String validateURL(String value) {
try {
return URLEncoder.encode(new URL(value).toString(), "UTF-8");
} catch (IOException e) {
return null;
}
}
/**
* If security is turned off, what is the default web user?
* @param conf the configuration to look in
* @return the remote user that was configuration
*/
public static UserGroupInformation getDefaultWebUser(Configuration conf
) throws IOException {
String[] strings = conf.getStrings(JspHelper.WEB_UGI_PROPERTY_NAME);
if (strings == null || strings.length == 0) {
throw new IOException("Cannot determine UGI from request or conf");
}
return UserGroupInformation.createRemoteUser(strings[0]);
}
private static InetSocketAddress getNNServiceAddress(ServletContext context,
HttpServletRequest request) {
String namenodeAddressInUrl = request.getParameter(NAMENODE_ADDRESS);
InetSocketAddress namenodeAddress = null;
if (namenodeAddressInUrl != null) {
namenodeAddress = NetUtils.createSocketAddr(namenodeAddressInUrl);
} else if (context != null) {
namenodeAddress = NameNodeHttpServer.getNameNodeAddressFromContext(
context);
}
if (namenodeAddress != null) {
return namenodeAddress;
}
return null;
}
/** Same as getUGI(null, request, conf). */
public static UserGroupInformation getUGI(HttpServletRequest request,
Configuration conf) throws IOException {
return getUGI(null, request, conf);
}
/** Same as getUGI(context, request, conf, KERBEROS_SSL, true). */
public static UserGroupInformation getUGI(ServletContext context,
HttpServletRequest request, Configuration conf) throws IOException {
return getUGI(context, request, conf, AuthenticationMethod.KERBEROS_SSL, true);
}
/**
* Get {@link UserGroupInformation} and possibly the delegation token out of
* the request.
* @param context the ServletContext that is serving this request.
* @param request the http request
* @param conf configuration
* @param secureAuthMethod the AuthenticationMethod used in secure mode.
* @param tryUgiParameter Should it try the ugi parameter?
* @return a new user from the request
* @throws AccessControlException if the request has no token
*/
public static UserGroupInformation getUGI(ServletContext context,
HttpServletRequest request, Configuration conf,
final AuthenticationMethod secureAuthMethod,
final boolean tryUgiParameter) throws IOException {
final UserGroupInformation ugi;
final String usernameFromQuery = getUsernameFromQuery(request, tryUgiParameter);
final String doAsUserFromQuery = request.getParameter(DoAsParam.NAME);
if(UserGroupInformation.isSecurityEnabled()) {
final String remoteUser = request.getRemoteUser();
String tokenString = request.getParameter(DELEGATION_PARAMETER_NAME);
if (tokenString != null) {
Token<DelegationTokenIdentifier> token =
new Token<DelegationTokenIdentifier>();
token.decodeFromUrlString(tokenString);
InetSocketAddress serviceAddress = getNNServiceAddress(context, request);
if (serviceAddress != null) {
SecurityUtil.setTokenService(token, serviceAddress);
token.setKind(DelegationTokenIdentifier.HDFS_DELEGATION_KIND);
}
ByteArrayInputStream buf = new ByteArrayInputStream(token
.getIdentifier());
DataInputStream in = new DataInputStream(buf);
DelegationTokenIdentifier id = new DelegationTokenIdentifier();
id.readFields(in);
if (context != null) {
final NameNode nn = NameNodeHttpServer.getNameNodeFromContext(context);
if (nn != null) {
// Verify the token.
nn.getNamesystem().verifyToken(id, token.getPassword());
}
}
ugi = id.getUser();
if (ugi.getRealUser() == null) {
//non-proxy case
checkUsername(ugi.getShortUserName(), usernameFromQuery);
checkUsername(null, doAsUserFromQuery);
} else {
//proxy case
checkUsername(ugi.getRealUser().getShortUserName(), usernameFromQuery);
checkUsername(ugi.getShortUserName(), doAsUserFromQuery);
ProxyUsers.authorize(ugi, request.getRemoteAddr(), conf);
}
ugi.addToken(token);
ugi.setAuthenticationMethod(AuthenticationMethod.TOKEN);
} else {
if(remoteUser == null) {
throw new IOException("Security enabled but user not " +
"authenticated by filter");
}
final UserGroupInformation realUgi = UserGroupInformation.createRemoteUser(remoteUser);
checkUsername(realUgi.getShortUserName(), usernameFromQuery);
// This is not necessarily true, could have been auth'ed by user-facing
// filter
realUgi.setAuthenticationMethod(secureAuthMethod);
ugi = initUGI(realUgi, doAsUserFromQuery, request, true, conf);
}
} else { // Security's not on, pull from url
final UserGroupInformation realUgi = usernameFromQuery == null?
getDefaultWebUser(conf) // not specified in request
: UserGroupInformation.createRemoteUser(usernameFromQuery);
realUgi.setAuthenticationMethod(AuthenticationMethod.SIMPLE);
ugi = initUGI(realUgi, doAsUserFromQuery, request, false, conf);
}
if(LOG.isDebugEnabled())
LOG.debug("getUGI is returning: " + ugi.getShortUserName());
return ugi;
}
private static UserGroupInformation initUGI(final UserGroupInformation realUgi,
final String doAsUserFromQuery, final HttpServletRequest request,
final boolean isSecurityEnabled, final Configuration conf
) throws AuthorizationException {
final UserGroupInformation ugi;
if (doAsUserFromQuery == null) {
//non-proxy case
ugi = realUgi;
} else {
//proxy case
ugi = UserGroupInformation.createProxyUser(doAsUserFromQuery, realUgi);
ugi.setAuthenticationMethod(
isSecurityEnabled? AuthenticationMethod.PROXY: AuthenticationMethod.SIMPLE);
ProxyUsers.authorize(ugi, request.getRemoteAddr(), conf);
}
return ugi;
}
/**
* Expected user name should be a short name.
*/
private static void checkUsername(final String expected, final String name
) throws IOException {
if (expected == null && name != null) {
throw new IOException("Usernames not matched: expecting null but name="
+ name);
}
if (name == null) { //name is optional, null is okay
return;
}
KerberosName u = new KerberosName(name);
String shortName = u.getShortName();
if (!shortName.equals(expected)) {
throw new IOException("Usernames not matched: name=" + shortName
+ " != expected=" + expected);
}
}
private static String getUsernameFromQuery(final HttpServletRequest request,
final boolean tryUgiParameter) {
String username = request.getParameter(UserParam.NAME);
if (username == null && tryUgiParameter) {
//try ugi parameter
final String ugiStr = request.getParameter("ugi");
if (ugiStr != null) {
username = ugiStr.split(",")[0];
}
}
return username;
}
/**
* Returns the url parameter for the given token string.
* @param tokenString
* @return url parameter
*/
public static String getDelegationTokenUrlParam(String tokenString) {
if (tokenString == null ) {
return "";
}
if (UserGroupInformation.isSecurityEnabled()) {
return SET_DELEGATION + tokenString;
} else {
return "";
}
}
/**
* Returns the url parameter for the given string, prefixed with
* paramSeparator.
*
* @param name parameter name
* @param val parameter value
* @param paramSeparator URL parameter prefix, i.e. either '?' or '&'
* @return url parameter
*/
public static String getUrlParam(String name, String val, String paramSeparator) {
return val == null ? "" : paramSeparator + name + "=" + val;
}
/**
* Returns the url parameter for the given string, prefixed with '?' if
* firstParam is true, prefixed with '&' if firstParam is false.
*
* @param name parameter name
* @param val parameter value
* @param firstParam true if this is the first parameter in the list, false otherwise
* @return url parameter
*/
public static String getUrlParam(String name, String val, boolean firstParam) {
return getUrlParam(name, val, firstParam ? "?" : "&");
}
/**
* Returns the url parameter for the given string, prefixed with '&'.
*
* @param name parameter name
* @param val parameter value
* @return url parameter
*/
public static String getUrlParam(String name, String val) {
return getUrlParam(name, val, false);
}
}