Close a resource in a Finally block from a try catch with resources

Question

I have in my code the next:

try (DockerClient client = DefaultDockerClient.fromEnv().connectTimeoutMillis(TimeUnit.SECONDS.toMillis(3)).build()) {
    //some code here
}catch (DockerCertificateException e) {
    log.warn("Failed to connect Docker Client {}", e.getMessage());
}
finally {

}

I need to close the client in the final block, but I can't because I'm getting an error (Cannot resolve symbol client).

Is there any way to close this client in the final block?

Why do you need to close it in the `finally` block if you're using try with resources? — Unmitigated, Oct 05 '21 at 18:05
Because inside the code could be some exceptions, I'm using the client inside the main try, but I need to close the connection at the end of whole process. — rasilvap, Oct 05 '21 at 18:11
@YuCheng Please post that as an answer and delete the comment. — Jim Garrison, Oct 05 '21 at 18:18

Yu Cheng · Answer 1 · 2021-10-05T18:28:41.027

1

The object in try(...) must implement AutoClosable and that object will be automatically closed whether or not an exception happens. You don't need the finally block at all.

If the object does not implement AutoClosable, you can fall back to the old try-catch-finally block as

DockerClient client = null;
try {
  //some code here
  client = DefaultDockerClient.fromEnv().connectTimeoutMillis(TimeUnit.SECONDS.toMillis(3)).build();
} catch (DockerCertificateException e) {
  log.warn("Failed to connect Docker Client {}", e.getMessage());
} finally {
  if (client != null) client.close();        
}

This is called the Java try-with-resources block. You can see an example that compares normal try-catch-finally block with the try-with-resources block here: https://www.baeldung.com/java-try-with-resources#replacing

edited Oct 05 '21 at 18:28

answered Oct 05 '21 at 18:19

Yu Cheng

131
1
3

The object is from a library, do you mean I have to create a wrapper which inherit from DockerClient and implement closeable? or something similar? – rasilvap Oct 05 '21 at 18:23
You can do that, but I suggest you simply use the old try-catch-finally block as shown in my edited answer. – Yu Cheng Oct 05 '21 at 18:26

score 1 · Accepted Answer · answered Oct 05 '21 at 18:52

1

Client will be closed, cause you are using try-with-resources (when you open resourse in try(resource definition)), which closes resource after try block automatically, you don`t need to write finally block.

answered Oct 05 '21 at 18:52

iggi

145
1
7

Close a resource in a Finally block from a try catch with resources

2 Answers2