CODEWITHSUNDEEP
java
William King
William King

Reputation: 13

Accessing variables and methods across threads

I am using java to create an interface to connect to a database. Each time I want to make a call to the database I need to create new connections to the database, which would make calling the database say 10 times slow.

To avoid having to create new connections each time I want to call the database I have a java thread running that holds all of the connection information.

To write/read from the database I want to create a thread that uses the connection information stored in the thread that's already running, use it to execute specified read/write functions, and then exit.

However I am having trouble accessing this information from the thread which is already running. What would be the best way to accomplish this?

Upvotes: 1

Views: 196

Answers (5)

Pascal Thivent
Pascal Thivent

Reputation: 570475

I would recommend to use a generic object pool instead of building your own solution and suggest to check Commons Pool from Apache Commons (this is an API for generic Object pooling, this isn't DBCP).

Upvotes: 0

Aravind Yarram
Aravind Yarram

Reputation: 80196

best way is not to re-invent the wheel. there are good open spource implementations of the connection pooling and i suggest you use them.

if you are already running in a container then use DataSource. look into c3p0 (http://sourceforge.net/projects/c3p0/) and commons-dbcp (http://commons.apache.org/dbcp/)

Upvotes: 1

hvgotcodes
hvgotcodes

Reputation: 120258

why are you doing this? There are frameworks, like Spring or equivalent, which will manage your connections for you. Don't reinvent the wheel man....

Upvotes: 0

duffymo
duffymo

Reputation: 308878

This is a terrible idea, because java.sql.Connection is not thread-safe.

A better idea would be to use a connection pool. Let each thread check out a connection, use it, and put it back.

Upvotes: 2

Jack
Jack

Reputation: 133609

Why do you need a thread running to keep your connection open, just store it somewhere and execute queries as soon as you need it.. should it work?

In any case if you really want a thread you should care about having a synchronized collection (check Collections.asSynchronizedList) that can be accessed and managed from your thread and others too.

To overcome visibility problems just declare it as a static final variable, so you won't have any problems in accessing it from outside the thread you declared it into.

Another easy solution (since connection seems to be not thread-safe) is not to use a thread but use just a monitor: you can easily manage a wait()/notify() mechanism for which a thread that wants to execute a query checks if connection is "free". if it is occupies the monitor and do whatever it wants before notifying all waiting threads.

Upvotes: 0

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