Tips and Tricks for Java

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Reading application properties with Spring

You can read complex env variables with Spring very easily. For example:

"VCAP_APPLICATION": {
    "uris": [
        "sample.url1.com",
        "sample.url2.com"
    ]
}

Retrieve the first URI from the uris array. In the application.yml file, type:

app:
   url: ${vcap.application.uris[0]:default}

Your code-config file should look like this:

@Configuration
public class Config {
    @Value("${app.url}")
    private String myAppUrl;
}

"sample.url1.com" will be inserted into the myAppUrl variable in Config class.

Enabling Java gc logs for CF application

cf set-env app-name JAVA_OPTS "-verbose:gc -XX:+PrintGCDetails"

cf restage app-name

Specifying heap and metaspace size for CF application

Use the newest version of Java buildpack (support for specifying heap size was added in 3.2):

cf push <APP-NAME> -p <ARTIFACT> -b https://github.com/cloudfoundry/java-buildpack.git

Set environment variables:

cf set-env <APP-NAME> JBP_CONFIG_OPEN_JDK_JRE: [memory_calculator: {memory_sizes: { heap: 64M, metaspace: 34M }}]

Restage application.