CODEWITHSUNDEEP
javajavascriptjdbcvert.x
Jack Sparser
Jack Sparser

Reputation: 75

How can I get data from JDBC + Java to Javascript with Vert.x?

I'm a noob with vertx, but I have already created the JDBC connection manager using a java class where I can print data from the result set: 

ConnectionManager cm=ConnectionManager.getInstance();
Connection conn = cm.getConnection();
try {
    Statement stmt=conn.createStatement();
    try {
        ResultSet rs =
        stmt.executeQuery("select username, password from users");              
        try {
            if (rs.next()){
                System.out.println(rs.getString(1));
            }
        } finally {
            rs.close();
        }

    } finally {
        stmt.close();
    }

} finally {
    conn.close();
}

Now I want to connect my vertx javascript app to this java class. I can't seem to get an idea where to start. I found a few sources from Google Groups, but none of them seem to shed some light:

Loading JDBC Drivers from JavaScript https://groups.google.com/forum/?fromgroups#!topic/vertx/_oJQaeH07Sg

Executing Java from Javascript https://groups.google.com/forum/#!msg/vertx/VyZj2yqqGTM/tvnTg4T55kMJ

I've also found a jdbc-persistor for Vert.x:

JDBC-persistor https://github.com/timyates/mod-jdbc-persistor/

I'm still trying to understand how to use it with my app. I will post whatever information I can share after, but for now, can anyone help me with this (persistor or direct java communication)? Thanks.

Upvotes: 1

Views: 3909

Answers (1)

Carlo Bertuccini
Carlo Bertuccini

Reputation: 20021

AFAIK the only way to do it is using the event bus. You put your Java code in a Verticle class (or in alternative create a module just for the goal). Something like this

public class JavaFromEverywhere extends Verticle {

    @Override
    public void start() throws Exception {
        vertx.eventBus().registerHandler("invokeFromAnyLanguage", new Handler<Message<String>>(){
            public void handle(Message<String> e) {
                doSomething();
            }

        });
    }

    private void doSomething() {
        // your database code here
    }

}

Then in your javascript you should just write

vertx.eventBus.send("invokeFromAnyLanguage", "");

This is a simple scenario. If you want do more complex things like sending to your JS the String received from the DB you can extend BusModBase and send back data. Meanwhile in your JS you should register an handler to handle the reply

public class JavaReply extends BusModBase {

    @Override
    public void start() {
        eb.registerHandler("invokeFromAnyLanguage", new Handler<Message<String>>(){
            public void handle(Message<String> e) {
                String something = doSomething();
                e.reply(something);
            }                
        });           
    }

    private String doSomething() {
        // your database code here
        return "databaseResult";
    }

}

and your JS code would be something like

eb.send("invokeFromAnyLanguage", "", function(javareply) {
    // your answer in javareply
});

HTH, Regards

Carlo

Upvotes: 2

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