4.4.1. Accessing JNDI over HTTP

This capability is provided by http-invoker.sar. The structure of the http-invoker.sar is:

http-invoker.sar
+- META-INF/jboss-service.xml
+- invoker.war
| +- WEB-INF/jboss-web.xml
| +- WEB-INF/classes/org/jboss/invocation/http/servlet/InvokerServlet.class
| +- WEB-INF/classes/org/jboss/invocation/http/servlet/NamingFactoryServlet.class
| +- WEB-INF/classes/org/jboss/invocation/http/servlet/ReadOnlyAccessFilter.class
| +- WEB-INF/classes/roles.properties
| +- WEB-INF/classes/users.properties
| +- WEB-INF/web.xml
| +- META-INF/MANIFEST.MF
+- META-INF/MANIFEST.MF

The jboss-service.xml descriptor defines the HttpInvoker and HttpInvokerHA MBeans. These services handle the routing of methods invocations that are sent via HTTP to the appropriate target MBean on the JMX bus.

The http-invoker.war web application contains servlets that handle the details of the HTTP transport. The NamingFactoryServlet handles creation requests for the JBoss JNDI naming service javax.naming.Context implementation. The InvokerServlet handles invocations made by RMI/HTTP clients. The ReadOnlyAccessFilter allows one to secure the JNDI naming service while making a single JNDI context available for read-only access by unauthenticated clients.

Figure 4.2. The HTTP invoker proxy/server structure for a JNDI Context

Before looking at the configurations let's look at the operation of the http-invoker services. Figure 4.2, “The HTTP invoker proxy/server structure for a JNDI Context” shows a logical view of the structure of a JBoss JNDI proxy and its relationship to the JBoss server side components of the http-invoker. The proxy is obtained from the NamingFactoryServlet using an InitialContext with the Context.INITIAL_CONTEXT_FACTORY property set to org.jboss.naming.HttpNamingContextFactory, and the Context.PROVIDER_URL property set to the HTTP URL of the NamingFactoryServlet. The resulting proxy is embedded in an org.jnp.interfaces.NamingContext instance that provides the Context interface implementation.

The proxy is an instance of org.jboss.invocation.http.interfaces.HttpInvokerProxy, and implements the org.jnp.interfaces.Naming interface. Internally the HttpInvokerProxy contains an invoker that marshalls the Naming interface method invocations to the InvokerServlet via HTTP posts. The InvokerServlet translates these posts into JMX invocations to the NamingService, and returns the invocation response back to the proxy in the HTTP post response.

There are several configuration values that need to be set to tie all of these components together and Figure 4.3, “The relationship between configuration files and JNDI/HTTP component” illustrates the relationship between configuration files and the corresponding components.

Figure 4.3. The relationship between configuration files and JNDI/HTTP component

The http-invoker.sar/META-INF/jboss-service.xml descriptor defines the HttpProxyFactory that creates the HttpInvokerProxy for the NamingService. The attributes that need to be configured for the HttpProxyFactory include:

InvokerName: The JMX ObjectName of the NamingService defined in the conf/jboss-service.xml descriptor. The standard setting used in the JBoss distributions is jboss:service=Naming.
InvokerURL or InvokerURLPrefix + InvokerURLSuffix + UseHostName. You can specify the full HTTP URL to the InvokerServlet using the InvokerURL attribute, or you can specify the hostname independent parts of the URL and have the HttpProxyFactory fill them in. An example InvokerURL value would be http://jbosshost1.dot.com:8080/invoker/JMXInvokerServlet. This can be broken down into:
- InvokerURLPrefix: the URL prefix prior to the hostname. Typically this will be http:// or https:// if SSL is to be used.
- InvokerURLSuffix: the URL suffix after the hostname. This will include the port number of the web server as well as the deployed path to the InvokerServlet . For the example InvokerURL value the InvokerURLSuffix would be :8080/invoker/JMXInvokerServlet without the quotes. The port number is determined by the web container service settings. The path to the InvokerServlet is specified in the http-invoker.sar/invoker.war/WEB-INF/web.xml descriptor.
- UseHostName: a flag indicating if the hostname should be used in place of the host IP address when building the hostname portion of the full InvokerURL. If true, InetAddress.getLocalHost().getHostName method will be used. Otherwise, the InetAddress.getLocalHost().getHostAddress() method is used.
ExportedInterface: The org.jnp.interfaces.Naming interface the proxy will expose to clients. The actual client of this proxy is the JBoss JNDI implementation NamingContext class, which JNDI client obtain from InitialContext lookups when using the JBoss JNDI provider.
JndiName: The name in JNDI under which the proxy is bound. This needs to be set to a blank/empty string to indicate the interface should not be bound into JNDI. We can't use the JNDI to bootstrap itself. This is the role of the NamingFactoryServlet.

The http-invoker.sar/invoker.war/WEB-INF/web.xml descriptor defines the mappings of the NamingFactoryServlet and InvokerServlet along with their initialization parameters. The configuration of the NamingFactoryServlet relevant to JNDI/HTTP is the JNDIFactory entry which defines:

A namingProxyMBean initialization parameter that maps to the HttpProxyFactory MBean name. This is used by the NamingFactoryServlet to obtain the Naming proxy which it will return in response to HTTP posts. For the default http-invoker.sar/META-INF/jboss-service.xml settings the name jboss:service=invoker,type=http,target=Naming.
A proxy initialization parameter that defines the name of the namingProxyMBean attribute to query for the Naming proxy value. This defaults to an attribute name of Proxy.
The servlet mapping for the JNDIFactory configuration. The default setting for the unsecured mapping is /JNDIFactory/*. This is relative to the context root of the http-invoker.sar/invoker.war, which by default is the WAR name minus the .war suffix.

The configuration of the InvokerServlet relevant to JNDI/HTTP is the JMXInvokerServlet which defines:

The servlet mapping of the InvokerServlet. The default setting for the unsecured mapping is /JMXInvokerServlet/*. This is relative to the context root of the http-invoker.sar/invoker.war, which by default is the WAR name minus the .war suffix.