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Serialization, class hierarchy and preserving sessions

If you have a class that implements Serializable, superclass fields do NOT get serialized unless the parent class also explicitly implements Serializable. That bit me the other day with session-scoped objects and preserving sessions across restarts, using Glassfish 3.1.1. Glassfish will complain if any objects in session scope or their properties don't implement serializable, but if those objects extend some parent class, the parent class fields are silently ignored and end up being null on session restore. So the source of the problem wasn't immediately clear, like it would have been if individual session objects or properties within them weren't serializable.
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Quick and dirty SSO with LTPA

If you have WebSphere application server in your environment, it is in fact possible to decode the “LtpaToken” cookie in code for quick-and-dirty SSO with non-WebSphere apps.

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Quick and dirty SSO with LTPA

If you have WebSphere application server in your environment, it is in fact possible to decode the "LtpaToken" cookie in code for quick-and-dirty SSO with non-WebSphere apps.

The main reason you might want to do this is if you have a portal-like application on WebSphere and want to link to other applications on different non-WebSphere servers.  This is only useful if WebSphere is your main point of entry.

Here's how you do it:

  • Export the LTPA encryption key to a file from WebSphere using the admin console.  You provide a passphrase and a filename.  
  • Find the "com.ibm.websphere.ltpa.3DESKey" value in the exported file.  This is the encrypted key.
  • Base64 decode the above key and decrypt with 3DES, using the passphrase provided.  The decrypted value is the actual key for decrypting LTPA tokens.
  • Take the "LtpaToken" cookie, base64 decode it, and decrypt it with the key.  The legacy LtpaToken cookie (which you can get with "interoperability mode") is encrypted with 3DES; the newer LtpaToken2 cookie uses AES.
  • Convert to String and parse.  The string looks like "values%expiration%signature" where the expiration is a standard UNIX timestamp, which you should use to ensure the token is still valid; and the values somewhere will contain the user DN (e.g., uid=user,ou=company,dc=com).
The Alfresco codebase contains a good example of how to do this in Java
http://svn.alfresco.com/repos/alfresco-open-mirror/alfresco/HEAD/root/modules/quickr/source/java/org/alfresco/repo/lotus/ws/impl/auth/LtpaAuthenticator.java

Relevant fragments of code:

private static final String AES_DECRIPTING_ALGORITHM = "AES/CBC/PKCS5Padding";
private static final String DES_DECRIPTING_ALGORITHM = "DESede/ECB/PKCS5Padding";

private byte[] getSecretKey(String ltpa3DESKey, String ltpaPassword) throws Exception
{
MessageDigest md = MessageDigest.getInstance("SHA");

md.update(ltpaPassword.getBytes());

byte[] hash3DES = new byte[24];

System.arraycopy(md.digest(), 0, hash3DES, 0, 20);

Arrays.fill(hash3DES, 20, 24, (byte) 0);

final Cipher cipher = Cipher.getInstance(DES_DECRIPTING_ALGORITHM);

final KeySpec keySpec = new DESedeKeySpec(hash3DES);

final Key secretKey = SecretKeyFactory.getInstance("DESede").generateSecret(keySpec);

cipher.init(Cipher.DECRYPT_MODE, secretKey);

byte[] secret = cipher.doFinal(Base64.decodeBase64(ltpa3DESKey.getBytes()));

return secret;
}

private byte[] decrypt(byte[] token, byte[] key, String algorithm) throws Exception
{
SecretKey sKey = null;

if (algorithm.indexOf("AES") != -1)
{
sKey = new SecretKeySpec(key, 0, 16, "AES");
}
else
{
DESedeKeySpec kSpec = new DESedeKeySpec(key);
SecretKeyFactory kFact = SecretKeyFactory.getInstance("DESede");
sKey = kFact.generateSecret(kSpec);
}
Cipher cipher = Cipher.getInstance(algorithm);

if (algorithm.indexOf("ECB") == -1)
{
if (algorithm.indexOf("AES") != -1)
{
IvParameterSpec ivs16 = generateIvParameterSpec(key, 16);
cipher.init(Cipher.DECRYPT_MODE, sKey, ivs16);
}
else
{
IvParameterSpec ivs8 = generateIvParameterSpec(key, 8);
cipher.init(Cipher.DECRYPT_MODE, sKey, ivs8);
}
}
else
{
cipher.init(Cipher.DECRYPT_MODE, sKey);
}
return cipher.doFinal(token);
}

private IvParameterSpec generateIvParameterSpec(byte key[], int size)
{
byte[] row = new byte[size];

for (int i = 0; i < size; i++)
{
row[i] = key[i];
}

return new IvParameterSpec(row);
}
// How to use it:
byte[] secretKey = getSecretKey(ltpa3DESKey, ltpaPassword);
byte[] ltpaTokenBytes = Base64.decodeBase64(ltpaToken.getBytes());
String token = new String(decrypt(ltpaTokenBytes, secretKey, DES_DECRIPTING_ALGORITHM));
// or
String token = new String(decrypt(ltpaTokenBytes, secretKey, AES_DECRIPTING_ALGORITHM));
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Bizarre Glassfish JSF/EL performance issue

I found a performance issue with JSF on Glassfish 3.1.1 (and prior) in an unexpected place: a seemingly innocuous line of code like

<h:outputText rendered="#{request.requestURL.indexOf('page') ne -1}" .... />

It turns out that invoking methods through EL expressions (new in EL 2.2) triggers creating a new ExpressionFactory, which in turn calls findResource/getResourceAsStream - a file I/O operation.

These expressions in the "rendered" attribute are particularly bad because they get executed multiple times in various parts of the JSF lifecycle.

See:
http://java.net/jira/browse/JAVASERVERFACES-2223
http://java.net/jira/browse/UEL-19

On the plus side - jvisualvm totally rocks.  I am shocked by how easy it was to get started with for tracking down these issues and it was right there in $JAVA_HOME/bin all along.
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Infinite loop in Glassfish exception logging

When Glassfish catches a ServletException, it calls getRootCause recursively on each successive unwrapped, nested exception by reflection.  This is fine for wrapped ServletException and JspException, which have well-defined semantics for this method, but creates a big problem if you have an application-defined exception that happens to use the same "getRootCause" name with different semantics.

So I created a Glassfish bug report:
http://java.net/jira/browse/GLASSFISH-17390

Related original bug in Tomcat, since fixed:
https://issues.apache.org/bugzilla/show_bug.cgi?id=39088
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Connecting Microstrategy 8


Connecting MicroStrategy 8.x Web SDK to a MicroStrategy 9.x Intelligence Server (iServer) doesn't work.  That in itself isn't a surprise.  What is surprising, though, is that the failure persists and then prevents the 8.x Web SDK from working with an 8.x iServer like it's supposed to on subsequent connections, resulting in an error "The required encryption level is not supported in this release."

Apparently, this is a result of initializing "static" fields on the first session creation, such that those values get stuck for the lifetime of the classloader.  In this case, the connection to 9.x sets some of these values in ways that are incompatible with 8.x.  If the first session creation is to an 8.x iServer, then there's no problem - attempting to connect to 9.x will break but won't prevent subsequent connections to 8.x.

This is an unusual edge case, to be sure.  I only encountered it during development in a heterogeneous environment, with a custom portal that connects to multiple iServers.
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solved windows 7 sleep problem

Sleep mode was grayed out on new Dell laptop (Latitude E6420) on Windows 7.

The fix was to disable the legacy VGA driver, which came up with a yellow warning icon in Device Manager ("device cannot start").

Simply installing the latest Intel Graphics drivers did not fix the issue - the legacy VGA driver had to be explicitly disabled.
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502 Proxy Error solved

I was getting mysterious, intermittent proxy errors using Apache mod_proxy to talk to an older version of Glassfish (2.x). It turned out the root cause was size of HTTP headers as cookies were accumulating, which caused the underlying app server to close the socket without a response.

A similar phenomenon was documented here:
http://kenai.com/jira/browse/KENAI-2727

The fix was trivial: increase the "receive-buffer-in-bytes" setting in domain.xml to 8192 bytes.

Finding it was a pain, because the older version of Glassfish had a bug such that the underlying IOException that aborted the request never got logged anywhere!
http://java.net/jira/browse/GLASSFISH-5181
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JSF + JPA without EJB or Spring

I've had success using JSF 2.0 with JPA on Glassfish 3.0.1, without using Spring or EJB for managing middle-tier services or DAOs. (I actually do like Spring - the goal in this case was to minimize dependencies, moving parts and learning curve, rather than to avoid any particular technology.)

A similar approach was detailed here:
http://www.swview.org/blog/best-way-use-jpa-web-tier

 Using only the JSF @ManagedBean and @ManagedProperty annotations, along with the JPA @PersistenceContext, you can refactor business services or DAOs into other JSF managed beans that are injected into the one exposed directly to the UI. What this looks like in practice:

 orders.xhtml:
 

OrderBean.java:
@ManagedBean
public class OrderBean {
@ManagedProperty(value="#{orderDao}")
private OrderDao orderDao;
private List orders;

@PostConstruct
public void init() {
this.orders = orderDao.getOrders();
}
public List getOrders() {
return orders;
}
}

OrderDao.java:
@ManagedBean
@ApplicationScoped
public class OrderDao {
@PersistenceContext(...)
private EntityManager em;

public List<Order> getOrders() {
return em.findAll(Order.class);
}
}
In this example, the DAO (OrderDao) is just another JSF managed bean, but not actually referenced directly from a page, only from another managed bean. This approach lets you isolate the logic tied to EntityManagers from the rest of your "normal" JSF managed beans, and makes it (marginally) easier to unit-test your managed beans because you can mock the DAO at a higher level instead of mocking the entity manager.

 This does NOT buy you declarative transactions or any of the other good stuff you get with Spring or EJB. (You can inject a UserTransaction with @Resource, and call it explicitly, though.) So it works best for simple apps with mostly read operations and basic single-object CRUD transactions.

 Also, with Java EE 6 CDI, all this may become moot because @Named and @Inject annotations effectively blur the line between all the different managed bean flavors (EJB, JSF, Spring/POJO), although I haven't found a good way to replace JSF @ViewScoped without buying into Seam.
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WebSphere "invalid Oracle URL specified" error


Another unhelpful WebSphere error, this time with an assist from Oracle.

This happened to me when I configured my JDBC data source with the default wpdbJDBC_oracle JDBC provider, using the XA datasource (OracleXADataSource), and used the "container managed" J2C authentication alias instead of "component managed".  The WebSphere admin console will successfully test the connection, but when you use it in a web application, it will fail with this "Invalid Oracle URL specified" error.  It was so hard to track down because it made me focus on the JDBC URL, which wasn't ever the problem.  It never occurred to me that the admin console and the web applications would somehow be getting connections and signing into Oracle differently, which tricked me into thinking that my configuration was really ok when it wasn't.

For the record, the web application was just doing a straight JNDI datasource lookup without any resource-ref mapping in web.xml, using the same JNDI name as bound in the server.

Also, changing to a different non-XA JDBC provider using plain OracleConnectionPoolDataSource resulted in "invalid username/password".

When I changed the datasource to use the component-managed alias instead, and restarted, everything worked.
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WebSphere Portal error - "Puma requested entity type Group from VMM but received Entity"

Got this error when trying to upgrade from WebSphere Portal 6.0 to 7.0.

com.ibm.portal.puma.SchemaViolationException: EJPSG0053E: Puma requested entity type Group from VMM but received Entity.

This sets a record for one of the most unhelpful errors ever. It can be caused by a bad entry in LDAP - in my particular case, it was a few groups whose objectClasses (groupOfUniqueNames and top) had somehow been saved with base-64 encoding instead of as plain text, although the values themselves when decoded were correct. The same exact LDAP directory was also working fine with WebSphere 6.0.

One of IBM's pages implies that the configuration itself is broken - when in my case, the configuration was perfectly fine and the problem was a bad entry in LDAP. The error gives no help tracking down the broken entry.

https://www-304.ibm.com/support/docview.wss?uid=swg21419580

Other IBM resources imply that the specific configuration issue is making sure that the group and user LDAP object classes are unique - i.e., don't use "top". In my case, I was doing pretty standard stuff - groupOfUniqueNames and inetOrgPerson.

http://publib.boulder.ibm.com/infocenter/wpzosdoc/v6r1/index.jsp?topic=/com.ibm.wp.msg.doc/messages/com.ibm.wps.puma.resources.Messages.html

https://www-304.ibm.com/support/docview.wss?uid=swg1PK80507
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Javascript, getYear and cookie expiration

Chrome and Firefox both return an offset from 1900 for date.getYear() instead of a four-digit year (pre-Y2K, a two-digit year). So new Date().getYear() returns 111 instead of 2011.

Old news, right? Well, I've been getting away with this for a while and not realizing it, in logic to expire cookies, and didn't notice until switching to Chrome.

The cookie expiration function was something like this

Date d = new Date();

d.setYear(d.getYear() - 1); // last year = 110
document.cookie = "COOKIE_NAME=; expires=" + d.toGMTString();

Firefox was happily setting the cookie's expiration to the year 0110, which was wrong but still accomplishing the end goal of expiring the cookie.

Chrome, on the other hand, mangled toGMTString to only print the three digits "110" and was not interpreting the cookie as expired.

Of course, the better question is why write this code yourself anyway, when jQuery, Dojo, etc., all have their own cookie APIs.
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Javascript associative array and iteration order

I just noticed that some browsers, like IE9 and Chrome, don't preserve insertion order of keys when iterating with a for-in loop ["for (key in array)"]. Although technically Javascript never guaranteed preserving order in a for-in loop, so many popular browsers did anyway that I was taken by surprise.

The Chrome behavior is especially odd - it preserves order of insertion for non-numeric keys, but iterates numeric keys in numeric order first. It also coerces numeric strings to numbers.

This code example illustrates

var foo=new Object();


foo["111_"] = 1;
foo["222_"] = 2;
foo["333_"] = 3;
foo["444"] = 4;
foo["555"] = 5;
foo["666"] = 6;

var str = "";
for (var key in foo) {
str = str + foo[key] + " ";
}
document.write(str);

In Chrome this prints "4 5 6 1 2 3". In IE 7, IE 8, and Firefox, it prints "1 2 3 4 5 6".

This behavior (particularly the coercion of numeric strings) has been tracked as a bug in Chrome - but unclear whether it will ever be fixed
http://code.google.com/p/chromium/issues/detail?id=37404

ECMAScript spec says "order of enumerating... is not defined"
http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf

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commons-logging classloader pain

I recently learned about commons-logging's classloader behavior the hard way when moving applications that use log4j from Tomcat to WebLogic. I had naively put commons-logging.jar in my WebLogic system classpath to emulate Tomcat's behavior, and things subsequently broke. This web site provided a very detailed and erudite explanation:

http://www.qos.ch/logging/classloader.jsp

Basically, it boils down to weird subtlety in commons-logging's behavior. If commons-logging.jar is in the system classpath in a J2EE environment, the "current" or "thread context" classloader for each individual webapp contains WEB-INF/lib, but commons-logging itself is loaded in the system (parent) classpath. commons-logging looks for log4j using the thread-context classloader and therefore will "see" log4j in WEB-INF/lib, but tries to actually load it in the system classpath, and breaks with a NoClassDefFoundError.

Various solutions:

  • Only put commons-logging-api.jar in the system classpath, as Tomcat does. (I didn't realize there were two different variations of the JAR at first. I know, RTFM.) This stripped-down commons-logging will pretend that log4j doesn't exist. Downside: logging output from third-party APIs like Hibernate, Digester, etc. will go who-knows-where, but not the same place as your application's log4j output.

  • Put log4j in the system classpath too. This works, but has the bad side effect that all applications will share a single log4j configuration and this makes logging unmanageable.

  • Put commons-logging.jar in your WEB-INF/lib directory. I'd heard bad things about this, especially if you want to deploy the same WAR in Tomcat. But for whatever reason it worked fine with Tomcat 4.1.31 and WebLogic 8.1. So this may be my preferred solution.



Anyhow, if this was confusing to someone who has been doing J2EE professionally for 5-6 years, I can imagine how confusing it must be to someone just trying to do this for the first time. The BileBlog puts it a lot less charitably.
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