why does the javax.naming.NamingException occur here?

Question

when i run the following :

package NonServletFiles;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javax.sql.DataSource;
import javax.naming.*;

public class GetTagsFromDatabase {

public GetTagsFromDatabase() {

}

public String[] getTags() {

    String tags[] = null;
    try {
        Context context = new InitialContext();
        DataSource ds = (DataSource)context.lookup("java:comp/env/jdbc/photog"); // <<----- line 23
        Connection connection = ds.getConnection();
        String sqlQuery = "select NAMEOFTHETAG from tagcollection";
        PreparedStatement statement = connection.prepareStatement(sqlQuery);
        ResultSet set = statement.executeQuery();

        int i = 0;
        while(set.next()) {
            tags[i] = set.getString("NameOfTheTag");
            System.out.println(tags[i]);
            i++;
        }
    }catch(Exception exc) {
        exc.printStackTrace();
    }

    return tags;
}

public static void main(String args[]) {
    new GetTagsFromDatabase().getTags(); // <<----- line 43
}
}

I get the following exceptions :

javax.naming.NamingException: Lookup failed for 'java:comp/env/jdbc/photog' in SerialContext[myEnv={java.naming.factory.initial=com.sun.enterprise.naming.impl.SerialInitContextFactory, java.naming.factory.url.pkgs=com.sun.enterprise.naming, java.naming.factory.state=com.sun.corba.ee.impl.presentation.rmi.JNDIStateFactoryImpl} [Root exception is javax.naming.NamingException: Invocation exception: Got null ComponentInvocation ]
at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:518)
at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:455)
at javax.naming.InitialContext.lookup(InitialContext.java:411)
at NonServletFiles.GetTagsFromDatabase.getTags(GetTagsFromDatabase.java:23)
at NonServletFiles.GetTagsFromDatabase.main(GetTagsFromDatabase.java:43)

Caused by: javax.naming.NamingException: Invocation exception: Got null ComponentInvocation 
at com.sun.enterprise.naming.impl.GlassfishNamingManagerImpl.getComponentId(GlassfishNamingManagerImpl.java:873)
at com.sun.enterprise.naming.impl.GlassfishNamingManagerImpl.lookup(GlassfishNamingManagerImpl.java:742)
at com.sun.enterprise.naming.impl.JavaURLContext.lookup(JavaURLContext.java:172)
at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:498)
... 4 more

I don't know the reason for this exception,all other servlets that need to connect to the database with the url java:comp/env/jdbc/photog work fine.

Answer 1

The stacktrace hints that you're using Glassfish. Remove the java:comp/env/ part. It's the default JNDI context root already. Only in Tomcat you need to specify it explicitly. Also, you should be invoking this in webapp context, not as a plain Java Application with main().

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Unrelated to the concrete problem, do you really need to get the DataSource everytime? I'd create a helper class which obtains it only once on webapp's startup or in a static initializer. It's application wide and threadsafe. Only the Connection indeed needs to be obtained (and closed! you're not closing it, so you're leaking DB resources) everytime you need to fire a SQL query.