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Common Problems (and Their Solutions) |
Class Not Found
Problem: You get NoClassDefFoundError when running your program.
Cause: You have not included the JNDI classes (jndi.jar) in your classpath, or you have not installed the JNDI classes properly.
Solution:
When using the Java 2 SDK, v 1.3, the JNDI classes are already included in the SDK. You should not be getting this error.
If you are not using the Java 2 SDK, v 1.3, the way you include the JNDI classes your execution environment depends on your execution environment. When using the Java 2 SDK, v 1.2, make sure that jndi.jar is in the JAVA_HOME/jre/lib/ext directory, where JAVA_HOME is the directory where the JRE has been installed. Note that on some platforms, there is a separate "jre/lib/ext" directory for the JRE and the SDK. Make sure that the JNDI jars have been installed in both "jre/lib/ext" directories. When using the JDK 1.1, using the java interpreter, you can either add the JARs to your CLASSPATH environment variable or add them to the -classpath option in your java command line.
For an applet, you need to make the JNDI and provider classes available to that applet (for example, by adding them to the archive option).
No Initial Context
Problem: You get NoInitialContextException.
Cause: You have not specified which implementation to use for the initial context. Specifically, the Context.INITIAL_CONTEXT_FACTORY
environment property has not been set to the class name of the factory that will create the initial context.
Or, you have not made the classes of the service provider named by Context.INITIAL_CONTEXT_FACTORY available to the program.
Solution: Set the Context.INITIAL_CONTEXT_FACTORY environment property to the class name of the initial context implementation you are using. See The Basics
trail for details.
If the property has been set, make sure the class name is not mistyped, and make sure that the class named is available to your program (in its classpath, or installed in the "jre/lib/ext" directory of the JRE). The Java 2 SDK, v 1.3 includes service providers for LDAP, COS naming, and the RMI registry. All other service providers must be installed and added to the execution environment.
Connection Refused
Problem: You get a CommunicationException indicating "connection refused".
Cause: This happens when the server and port identified by the Context.PROVIDER_URL environment property is not being served by the server. Perhaps someone has disabled or turned off the machine on which the server is running. Perhaps you have mistyped the server's name or port number.
Solution: Check that there is indeed a server running on that port and restart the server if necessary. The way you perform this check depends on the LDAP server that you are using. Usually, there is an administrative console or tool that you use to administer the server. You may use that to verify the server's status.
Connection Fails
Problem: The LDAP server is responding to other utilities (such as its administration console) but does not seem to respond to your program's requests.Cause: The server does not respond to the LDAP v3 connection requests. Some servers (especially public servers) do not respond correctly to the LDAP v3 and just ignores the requests instead of rejecting them. Or, some LDAP v3 servers have problems handling a control that Sun's LDAP service provider automatically sends, and return oftentimes a server-specific failure code.
Solution. Try setting the environment property "java.naming.ldap.version" to "2". The LDAP service provider by default attempts to connect to an LDAP server using the LDAP v3 and, if that fails, it uses the LDAP v2. If the server silently ignores the v3 request, the provider will assume that the v3 request worked. To work around such servers, you must explicitly set the protocol version to ensure proper behavior on the part of the server.
If the server is a v3 server, try setting the following environment property before creating the initial context:
This will turn off the control that the LDAP provider sends automatically. (See the Referralsenv.put(Context.REFERRAL, "throw");lesson for details).
Program Hangs
Problem: The program just hangs.
Causes: Some servers (especially public ones) won't respond (not even with a negative answer) if you attempt to perform a search that would generate too many results or that would require the server to examine too many entries in order to generate the answer. Such servers are trying to limit the amount of resources they expend on a per-request basis.
Another cause is if you try to use Secure Socket Layer (SSL) against a server/port that does not support it, and vice versa (that is, by using a plain socket to talk to an SSL port).
Solution: If your program is hanging because the server is trying to restrict the use of its resources, you should retry your request using a query that will return a single result or only a few results. This will help you determine whether the server is alive. You can then broaden your initial query and resubmit it.
If your program is hanging because of SSL problems, you need to find out whether the port is an SSL port and then set the Context.SECURITY_PROTOCOL
Name Not Found
Problem: You get NameNotFoundException.
Causes: When you initialize the initial context for the LDAP, you supply a root distinguished name. For example, if you set the Context.PROVIDER_URL environment property for the initial context to "ldap://ldapserver:389/o=JNDITutorial", and subsequently supply a name like "cn=Joe,c=us", the full name that you are passing to the LDAP service is "cn=Joe,c=us,o=JNDITutorial". If this is really the name you intended, then you should check your server to make sure that it contains such an entry.
The Netscape Directory Server also returns this error if you supply an incorrect distinguished name for authentication purposes. For example, if you set Context.SECURITY_PRINCIPAL
Solution: You should verify that the name you supplied is that of an entry that exists on the server. You can do so by listing the entry's parent context or using some other tools such as the directory server's administration console.
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Common Problems (and Their Solutions) |