TypeSafe config & HOCON + Read JSON properties in java (example)

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  • Given a java application, We would like to read the property file defined in HOCON (Human-Optimized Config Object Notation.)  or JSON format.
  • The property files use the suffix .conf e.g. application.conf, reference.conf.
  • We are performing following operations:
    • Reading the JSON property file defined in reference.conf file.
    • Substituting environment variable in reference conf file.
      • java_directory = ${?JAVA_HOME}
    • We have created runnable jar to invoke main method of jar.
    • We are logging the properties using slf4j-log4j12.

TypeSafe Config Maven dependency:

<dependency>
    <groupId>com.typesafe</groupId>
    <artifactId>config</artifactId>
    <version>1.3.0</version>
</dependency>

Property file in HOCON/JSON format (reference.conf file)

userInfo {
    name=Mike
    age = 30
    roles = [
        guest
        read-only
    ]  
}
database {
 user=admin
 password=admin
}
//Read environment variable
java_directory = ${?JAVA_HOME}

Program to read HOCON or JSON property file in java

We are loading reference.conf using ConfigFactory.load()

package org.learn.application;
 
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
 
import com.typesafe.config.Config;
import com.typesafe.config.ConfigFactory;
 
public class Application {
    private static final Logger logger = LoggerFactory.getLogger(Application.class);
    private static final Config config = ConfigFactory.load();
    public static void main(String[] args) {
         
        logger.info("Start Reading HOCON file:");
 
        logger.info("UserName={}",config.getString("userInfo.name"));
        logger.info("age={}",config.getInt("userInfo.age"));
        logger.info("Array of roles={}",config.getStringList("userInfo.roles"));
         
        logger.info("Database userName={}",config.getString("database.user"));
        logger.info("Database password={}",config.getString("database.password"));
         
        //Read environment variable
        if(config.hasPath("java_directory")) {
            logger.info("Java installed directory={}",config.getString("java_directory"));
        }
         
        logger.info("End reading HOCON file");
    }
}

Output – Read HOCON or JSON config file in java

2016-07-06 21:09:58,754 [INFO] org.learn.application.Application [main] Start Reading HOCON file:
2016-07-06 21:09:58,759 [INFO] org.learn.application.Application [main] UserName=Mike
2016-07-06 21:09:58,760 [INFO] org.learn.application.Application [main] age=30
2016-07-06 21:09:58,761 [INFO] org.learn.application.Application [main] Array of roles=[guest, read-only]
2016-07-06 21:09:58,761 [INFO] org.learn.application.Application [main] Database userName=admin
2016-07-06 21:09:58,761 [INFO] org.learn.application.Application [main] Database password=admin
2016-07-06 21:09:58,761 [INFO] org.learn.application.Application [main] Java installed directory=C:\Program Files\Java\jdk1.8.0_60
2016-07-06 21:09:58,761 [INFO] org.learn.application.Application [main] End reading HOCON file

 

Download Code – TypeSafe/Config HOCON Java Application

 

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