在不同类别之间共享对象

Question

I need some "design" advise. I have static JDBC objects and my "main entry class" which are shared among other classes.

My MainClass looks like this:

public static Jdbc db1;
public static Jdbc db2;

connectDb(makeDirectConnection) // depending on runtime passed argument

public static connectDb(boolean makeDirectConnection) {
if(makeDirectConnection) // use direct connection
    db1 = JdbcFactory.getInstance("db/config/main/db1.properties");
    db2 = JdbcFactory.getInstance("db/config/main/db2.properties");
} else { // connect using via SSH tunnel (different host and port)
    db1 = JdbcFactory.getInstance("db/config/tunnel/db1.properties");
    db2 = JdbcFactory.getInstance("db/config/tunnel/db2.properties");
}

JdbcFactory maintains Map of instances.

It kinda works ok, but if I want to make unit test for classes where db1 or db2 is being used I get null pointer exception if from unit test I don't do MainClass.dbConnect()

Make thing worse - from test classes I need even one more different DB setup, so from Test.class I do:

Main.db1 = JdbcFactory.getInstance("db/config/test/db1.properties");

All together it's messy and I don't like. Isn't there some nicer approach how to share db1 and db2 ?

Also boolean makeDirectConnection which is defined from java run argument stops me from using final db1 and db2 . Any advice how to workaround this? (It depends on environment where program is executed - but I don't want to make it dependable on hostname or some other OS thing.

Answer 1

I would not provide a boolean as the jvm argument to differ between your two (or three) cases. Instead i would provide the db urls via paramter. In that case you can also call your method within your test with the "test-db.properties".

Answer 2

Since you are need to set the default instance diffrently for testing and deployment. So create a property file which mentiones that which file should be used to create default instance for db1 and db2 .

To remove the need of calling MainClass.dbConnect() from your unit test code, just create a static block and here initlize db1 and db2 with default. eg If property file is defaultDB.properties and having following content:

DB1=db/config/test/db1.properties
DB2=db/config/test/db2.properties

then use following:

static private Properties prop;
static {
    prop = new Properties();
    prop.load(new FileInputStream("defaultDB.properties"));
    db1 = JdbcFactory.getInstance(prop.getProperty("DB1"));
    db2 = JdbcFactory.getInstance(prop.getProperty("DB2"));
}