来自具有JNDI的其他IP服务器的spring.datasource.jndi-name

Question

I am developed a service that use the DataSource from a local JNDI (Server where to live the service and the JNDI).

In Spring boot this information is declared like this:

spring: datasource:
jndi-name: java:/comp/env/jdbc/MyLocalDB

I want to know if is possible to do something like this:

spring: datasource:
jndi-name: java:192.168.0.1:8080/comp/env/jdbc/MyLocalDB

Thanks

Answer 1

JNDI is an API to access directories. Application servers include directories to maintain information of the applications, the datasources and the EJB beans. JNDI can be used to access other types of directories. For instance, it can be used to access user information on Active Directoy and LDAP directory servers.

You can create client programs that access these JNDI directories and obtain data such as configuration data and RMI remote references to invoke EJB beans.

Accessing remote JNDI directories

If you are creating a client program, you can define an InitialContext describing the JNDI directory your program will use. You must define a Hashtable with the configuration, defining a Context.PROVIDER_URL and create the InitialContext .

For instance, you can create a program that access information in an LDAP directory .

// Set up the environment for creating the initial context
Hashtable<String, Object> env = new Hashtable<String, Object>();
env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
env.put(Context.PROVIDER_URL, "ldap://localhost:389/o=JNDITutorial");

// Create the initial context
DirContext ctx = new InitialDirContext(env);

// ... do something useful with ctx

Depending on the library you use, you can define a configuration file describing the JNDI remote host. For instance, for the JBoss EJB Client library , you can define a jboss-ejb-client.properties file. Glassfish uses a jndi.properties file .

Accessing remote resources

A resource is data (eg an image, audio, or text) that a program needs to access independently of the location of the program code. You can use the JNDI API or the @Resource annotation to access the information.

For instance, you can use the API to ask for data of users in an LDAP directory.

try {

    // Create the initial directory context
    DirContext ctx = new InitialDirContext(env);

    // Ask for all attributes of the object 
    Attributes attrs = ctx.getAttributes("cn=Ted Geisel, ou=People");

    // Find the surname attribute ("sn") and print it
    System.out.println("sn: " + attrs.get("sn").get());

} catch (NamingException e) {
    System.err.println("Problem getting attribute:" + e);
}

Accessing remote EJBs

You can access EJBs with remote interfaces located in other VMs . On the one hand, you must create the EJBs using CORBA-style remote interfaces and register the EJBs in the java: namespace in the server. On the other hand, the applications can use a corbaname URL to access these beans.

In Websphere/Liberty, if you define an EJB bound to:

java:global/ExampleApp/ExampleModule/ExampleBean!com.ibm.example.ExampleRemoteInterface
java:app/ExampleModule/ExampleBean!com.ibm.example.ExampleRemoteInterface    
java:module/ExampleBean!com.ibm.example.ExampleRemoteInterface

You can access remotely the EJB using RMI-IIOP (to invoke methods)

corbaname::test.ibm.com:2809#ejb/global/ExampleApp/ExampleModule/ExampleHomeBean!com.ibm.example.ExampleEJBHome
corbaname:rir:#ejb/global/ExampleApp/ExampleModule/ExampleHomeBean!com.ibm.example.ExampleEJBHome

Detailed configuration of these remote EJBs may vary from one application server to another. If you use Glassfish, you can check the documentation . There is an example in the Oracle blogs .

If you configure a cluster, there are many other options to access the remote resources using the names of the nodes in the cluster.

Accessing a remote Datasources

Datasources defined in a server cannot be accessed remotely. If you want to keep the configuration of the datasources in the JNDI directory, you can solutions define a custom class that implements the DataSource interface . A client can obtain the datasource configuration from the server and create a local database connection using that connection.