Learn how to use Java Logging API with EMA Java
The original article can be found on the Refinitiv Developers Community website.
The Enterprise Message API is an open source, data-neutral, multi-threaded, ease-of-use API providing access to OMM and RWF data. As part of the Refinitiv Real-Time Software Development Kit, or RTSDK, the Enterprise Message API allows applications to consume and provide Open Message Model data at the message level of the API stack.
EMA Java uses the Simple Logging Facade for Java (SLF4J) logging API to log information, and error messages for the following classes (loggers):
· com.refinitiv.ema.access.OmmConsumerImpl
· com.refinitiv.ema.access.OmmIProviderImpl
· com.refinitiv.ema.access.OmmNiProviderImpl
This article introduces SLF4J and demonstrates how to use it with Java Logging API.
Simple Logging Facade for Java
Simple Logging Facade for Java uses a simple façade pattern to offer a generic API for different logging frameworks (e.g., java.util.logging, logback, Log4j). It allows end users to select the desired logging framework when deploying applications. The SLF4J package contains several jar files referred to as “SLF4J provider” and each provider supports a corresponding framework. For example:
To change logging frameworks, users just replace slf4j providers on an application’s classpath. For example, to switch from java.util.logging to reload4j, just replace slf4j-jdk14.jar with slf4j-reload4j.jar.
The following diagram shows how the SLF4J providers work.
For the full diagram, please refer to the SLF4J user manual.
The next section will focus on how to configure and use EMA Java with the SLF4J JDK logging provider (slf4-jdk14.jar).
Java Logging API (java.util.logging)
Java Logging API was introduced in JDK 1.4. When using JDK 1.4 or higher, developers can use the built-in logging package provided by the java.util.logging package to log application messages.
SLF4J supports Java Logging API through the SLF4J provider for java.util.logging (slf4j-jdk.jar). To use the Java Logging API with slf4j, users just add or replace the slf4j-jdk.jar file on an application’s classpath.
EMA Java provides the slf4j-jdk.jar file in the Refinitiv Real-Time SDK package. It is in the RTSDK-BinaryPack\Java\Eta\Libs\SLF4J\slf4j-xxx directory. For example:
Developers can enable Java Logging API via configurations or create custom log handlers to process log entries.
Java Logging API Configurations
The Java logging API (java.util.logging) loads configurations from the logging.properties file. By default, Java 8 locates this file in the $JAVA_HOME/jre/lib/ directory while Java 9 and above locate this file from $JAVA_HOME/conf. However, developers can overwrite this via the JVM arguments or coding.
- Load the logging.properties file via coding
The following code can be used to load the logging.properties file.
LogManager.getLogManager().readConfiguration(new FileInputStream("logging.properties"));- Load the logging.properties file via the JVM arguments
The logging.properties file can also be specified via the java.util.logging.config.file argument.
-Djava.util.logging.config.file=logging.propertiesLogging.properties
Users specify active handlers and handlers’ settings in the logging.properties file. Here is an example of a Java Logging API configuration file.
handlers=java.util.logging.ConsoleHandler, java.util.logging.FileHandler
.level=FINEST
java.util.logging.ConsoleHandler.level=FINEST
java.util.logging.ConsoleHandler.formatter=java.util.logging.SimpleFormatter
java.util.logging.FileHandler.level=FINEST
java.util.logging.FileHandler.pattern= %h/java%u.log
java.util.logging.FileHandler.limit=50000000
java.util.logging.FileHandler.count=20
java.util.logging.FileHandler.formatter=java.util.logging.SimpleFormatter
java.util.logging.SimpleFormatter.format=%1$tY-%1$tm-%1$td %1$tH:%1$tM:%1$tS.%1$tL %4$-7s %2$s %n%5$s
Custom Log Handlers
Instead of using the java.util.logging.ConsoleHandler or java.util.logging.FileHandler to get logging messages, developers can implement custom log handlers to retrieve logging messages from Java Logging API.
Define a custom handler
Custom Log Handlers inherit from java.util.logging.Handler. A java.util.logging.Handler object takes log messages from a Logger and exports them.
The handler can override the publish method to retrieve the logging messages. LogRecord objects are used to pass logging requests between the logging framework and individual log Handlers so developers can access logging messages from the LogRecord objects. For example, the code below gets the logging message level, the source logger’s name, and the log message from the LogRecord object. Then, print them to standard output.
import java.util.logging.Handler;
import java.util.logging.LogRecord;
public class MyLogHandler extends Handler{
@Override
public void publish(LogRecord record) {
// TODO Auto-generated method stub
System.out.println("##### Log: "+record.getLoggerName()+" #####");
System.out.println("Level: "+ record.getLevel());
System.out.println("Message: \n"+ record.getMessage());
}
@Override
public void flush() {
// TODO Auto-generated method stub
}
@Override
public void close() throws SecurityException {
// TODO Auto-generated method stub
}
}Add a custom handler
A custom handler must be added to a logger to receive logging messages. It can be added to a logger via coding or the handlers configuration.
Use the code below to add a custom handler.
import java.util.logging.Handler;
import java.util.logging.LogManager;
import java.util.logging.Logger;
…
Logger rootLogger = LogManager.getLogManager().getLogger("");
rootLogger.addHandler(new MyLogHandler());
...The code calls the getLogger(“”) method to get the root logger, and then adds a custom handler to the root logger.
Otherwise, a custom handler can be specified in the logging.properties file by adding its class name to the handlers configuration.
handlers=MyLogHandler
.level=FINEST
…
…After that, the following logging messages from the custom handler (MyLogHandler) will be printed to the console.
##### Log: com.refinitiv.ema.access.OmmConsumerImpl #####
Level: FINEST
Message:
loggerMsg
ClientName: Consumer_1_1
Severity: Trace
Text: Successfully created Reactor.
loggerMsgEnd
##### Log: com.refinitiv.ema.access.OmmConsumerImpl #####
Level: FINEST
Message:
loggerMsg
ClientName: LoginCallbackClient
Severity: Trace
Text: Created LoginCallbackClient
loggerMsgEndSummary
EMA Java uses the Simple Logging Facade for Java (SLF4J) logging API which is a generic API for different logging frameworks (e.g., java.util.logging, logback, Log4j). This article focuses on how to use SLF4J logging API with Java Logging API (java.util.logging). Users can either enable Java Logging API via configurations (logging.properties) or create custom log handlers to process log entries.
References
1. Docs.oracle.com. n.d. ConsoleHandler (Java SE 11 & JDK 11 ). [online] Available at: <https://docs.oracle.com/en/java/javase/11/docs/api/java.logging/java/util/logging/ConsoleHandler.html> [Accessed 23 September 2022].
2. Docs.oracle.com. n.d. FileHandler (Java SE 11 & JDK 11 ). [online] Available at: <https://docs.oracle.com/en/java/javase/11/docs/api/java.logging/java/util/logging/FileHandler.html> [Accessed 23 September 2022].
3. Docs.oracle.com. n.d. Formatter (Java SE 11 & JDK 11 ). [online] Available at: <https://docs.oracle.com/en/java/javase/11/docs/api/java.logging/java/util/logging/Formatter.html> [Accessed 23 September 2022].
4. Docs.oracle.com. n.d. Handler (Java SE 11 & JDK 11 ). [online] Available at: <https://docs.oracle.com/en/java/javase/11/docs/api/java.logging/java/util/logging/Handler.html> [Accessed 23 September 2022].
5. https://mkyong.com/. 2021. Java Logging APIs Tutorial. [online] Available at: <https://mkyong.com/logging/java-logging-apis-tutorial/> [Accessed 23 September 2022].
6. Digitalocean.com. 2022. Logger in Java — Java Logging Example | DigitalOcean. [online] Available at: <https://www.digitalocean.com/community/tutorials/logger-in-java-logging-example> [Accessed 23 September 2022].
7. Docs.oracle.com. n.d. LogManager (Java SE 11 & JDK 11 ). [online] Available at: <https://docs.oracle.com/en/java/javase/11/docs/api/java.logging/java/util/logging/LogManager.html> [Accessed 23 September 2022].
8. Docs.oracle.com. n.d. LogRecord (Java SE 11 & JDK 11 ). [online] Available at: <https://docs.oracle.com/en/java/javase/11/docs/api/java.logging/java/util/logging/LogRecord.html> [Accessed 23 September 2022].
9. Developers.refinitiv.com. 2022. Refinitiv Real-Time Java SDK. [online] Available at: <https://developers.refinitiv.com/en/api-catalog/refinitiv-real-time-opnsrc/rt-sdk-java> [Accessed 23 September 2022].
10. Slf4j.org. 2022. SLF4J Manual. [online] Available at: <https://www.slf4j.org/manual.html> [Accessed 23 September 2022].
