JarCastingSpring Auto-Configuration Library
This library provides the following features:
-
Dynamic properties access
-
JMX Bean detection and configuration
Adding Configuration
The provided @Configuration classes in this library can be enabled in your application by using one of the following options:
@Import
Use the @Import annotation on your primary configuration class to include the specific configuration class you wish to add:
@Configuration
@Import(PropertyLoaderConfigurator.class)
public class AppConfig { }
@ComponentScan
Use the @ComponentScan annotation on your primary configuration to include all configuration classes within the specified package:
@Configuration
@ComponentScan(basePackages = { "com.your.package", "com.buabook.spring.configuration" })
public class AppConfig { }
Dynamic Property Loader
Most of the time, Spring's @Value annotation allows you to assign configuration from a properties file into a variable and use it.
There are some usecases where you need to dynamically generate the property name before it and then load it. The PropertyLoader class provides provides this. The PropertyLoaderConfigurator will configure this class for you. Simply autowire the property loader to use it:
@Component
public class UrlResolver {
@Autowired
private PropertyLoader properties;
private String getSiteUrlFor(String provider) {
return properties.getProperty("buabook.site." + provider);
}
}
JMX Bean Detection
The JmxConfigurator configuration class will automatically register all classes that implement the IExposeToJmx interface to Spring in order for it to expose it to JMX.
The IExposeToJmx interface requires no methods to be implemented, it just provides a way for Spring to detect the classes. The following annotations should be used to expose data to JMX:
@ManagedResourceon the class@ManagedAttributeto return data to JMX@ManagedOperationto define a method as executable via JMX@ManagedOperationParameterto define each parameter required for a JMX-exposed method
@Component
@ManagedResource(
objectName="com.buabook.spring.example:name=JMX Example",
description="Provides an example JMX class"
)
public class JmxExample implements IExposeToJmx {
@ManagedAttribute(description="Current time in milliseconds")
public Long getCurrentTimeMillis() {
return System.currentTimeMillis();
}
@ManagedOperation(description="Get system environment variable")
@ManagedOperationParameter(name="Environment variable")
public String getEnvironmentVariable(String envName) {
return System.getenv(envName);
}
}
Once a class has been correctly configured for JMX, you should lines like the following in your log:
2017-01-06 15:14:56.392 INFO 6792 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Bean with name 'apiInterfaceManagement' has been autodetected for JMX exposure
2017-01-06 15:14:56.396 INFO 6792 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Located managed bean 'apiInterfaceManagement': registering with JMX server as MBean [com.buabook.api_interface:name=API Interface Control]
Enabling JMX
Once you have JMX MBeans configured, you need to also configure Java to listen for JMX connections so you can connect via Java Mission Control or similar application.
To do this with no password or SSL authentication, use the following Java arguments as part of your application start command:
-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=$JMX_PORT -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Djava.rmi.server.hostname=$(hostname -I)
In our experience you should specify the hostname as the IP address of the host (which hostname -I will do on Ubuntu servers).
