zero-di.md

Dependency Injection ( JSR 330 )

To avoid object relationship complex, zero also support Simple dependency injection based on JSR 330.

Vert.x Way

All the vert.x specific object could be inject as following way.

import javax.inject.infix.Mongo;
import javax.inject.infix.MySql;
import javax.ws.rs.BodyParam;
import javax.ws.rs.POST;
import javax.ws.rs.Path;

@EndPoint
public class InjectApi {

    @MySql
    private transient SQLClient sqlClient;
    
    @Mongo
    private transient MongoClient mongo;
    // ......
}

The following object is supported by current zero version

• javax.inject.infix.@Mongo: io.vertx.ext.mongo.MongoClient
• javax.inject.infix.@MySql: io.vertx.ext.sql.SQLClient

Common Way ( JSR 330 )

1. Class implementation

Target Class

import io.vertx.ext.mongo.MongoClient;
import io.vertx.up.commune.Envelop;

import javax.inject.infix.Mongo;

public class InjectDao {

    @Mongo
    private transient MongoClient client;

    public void async(final Envelop envelop) {
        System.out.println(this.client);
    }
}

Inject InjectDao

import javax.inject.Inject;

@Queue
public class InjectWorker {

    @Inject
    private transient InjectDao dao;
    // ......
}

2. Interface with Unique implementation

Interface Definition

public interface InjectStub {

}

Implementation Class

public class InjectInstance implements InjectStub {

}

Inject InjectStub -> InjectInstance

import javax.inject.Inject;

@Queue
public class InjectWorker {

    @Inject
    private transient InjectStub stub;
    // ......
}

*: One limitation for this situation is that there are only one implementation of interface InjectStub.

3. Interface with Multi implementations

Interface Definition

public interface InjectA {
}

Implementation Class

InjectB

import javax.inject.Named;

@Named("NameInjectA")
public class InjectB implements InjectA {
}

InjectC

@Named
public class InjectC implements InjectA {
}

Inject InjectA -> InjectB

import io.vertx.up.annotations.Qualifier;
import javax.inject.Inject;

@Queue
public class InjectWorker {

    @Inject
    @Qualifier("NameInjectA")
    private transient InjectA injectA;

You can use @Qualifier to set which implementation should be inject.

Rules

• All this kind of classes are initialized with singleton mode, you shouldn't inject Value Object, POJO.
• All the injection points are based on some part of JSR330 but not all.