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Overwrite properties file if command line value is present

I have a program that will read everything from a file config.propertiesif there are no arguments on the command line other than the location of the config.properties file. Below is my config.properties file -

NUMBER_OF_THREADS: 100
NUMBER_OF_TASKS: 10000
ID_START_RANGE: 1
TABLES: TABLE1,TABLE2

If I run my program from the command line, for example:

java -jar Test.jar "C:\\test\\config.properties"

It should read all four properties from the file config.properties. But suppose if I run my program like this:

java -jar Test.jar "C:\\test\\config.properties" 10 100 2 TABLE1 TABLE2 TABLE3

then it should read all the properties from the arguments and overwrite the properties in the config.properties file.

Below is my code that works great in this scenario -

public static void main(String[] args) {

        try {

            readPropertyFiles(args);

        } catch (Exception e) {
            LOG.error("Threw a Exception in" + CNAME + e);
        }
    }

    private static void readPropertyFiles(String[] args) throws FileNotFoundException, IOException {

        location = args[0];

        prop.load(new FileInputStream(location));

        if(args.length >= 1) {
            noOfThreads = Integer.parseInt(args[1]);
            noOfTasks = Integer.parseInt(args[2]);
            startRange = Integer.parseInt(args[3]);

            tableName = new String[args.length - 4];
            for (int i = 0; i < tableName.length; i++) {
                tableName[i] = args[i + 4];
                tableNames.add(tableName[i]);
            }
        } else {
            noOfThreads = Integer.parseInt(prop.getProperty("NUMBER_OF_THREADS").trim());
            noOfTasks = Integer.parseInt(prop.getProperty("NUMBER_OF_TASKS").trim());
            startRange = Integer.parseInt(prop.getProperty("ID_START_RANGE").trim());
            tableNames = Arrays.asList(prop.getProperty("TABLES").trim().split(","));
        }

        for (String arg : tableNames) {

            //Some Other Code

        }
    }

Problem: -

Now what I'm trying to do is suppose someone starts a program like this

java -jar Test.jar "C:\\test\\config.properties" 10

noOfThreads -

noOfThreads should be 10 instead of 100

​​ -

java -jar Test.jar "C:\\test\\config.properties" 10 100

noOfThreads noOfTasks -

noOfThreads should be 10 instead of 100
noOfTasks should be 100 instead of 10000

.

- , ?

+5
3

.

List<String> paramNames = new ArrayList<String>{"NUMBER_OF_THREADS", "NUMBER_OF_TASKS", 
            "ID_START_RANGE", "TABLES"}; // Try to reuse the names from the property file
Map<String, String> paramMap = new HashMap<String, String>();
...
// Validate the length of args here
...
// As you table names can be passed separately. You need to handle that somehow. 
// This implementation would work when number of args will be equal to number of param names
for(int i = 0; i< args.length; i++) {
   paramMap.put(paramNames[i], args[i]); 
}

props.putAll(paramMap);
... // Here props should have it values overridden with the ones provided
+2

java -jar Test.jar "C:\\test\\config.properties" 10 100

, noOfThreads noOfTasks.

, , , . : -

java -jar -Dconfig.file.location="C:\\test\\config.properties" -DNUMBER_OF_THREADS=10 Test.jar

.

  • Properties.
  • System.getProperty().
  • , .

, , , .

PropertyUtil, , getIntProperty(), getStringProperty() ..

import java.io.FileInputStream;
import java.io.IOException;
import java.util.Properties;

public class PropertyUtil {

  private static final String DEFAULT_CONFIG_FILE_LOCATION = "config.properties";

  private String configFileLocation;

  private Properties properties;

  public PropertyUtil() throws IOException {

    this(DEFAULT_CONFIG_FILE_LOCATION);
  }

  public PropertyUtil(String configFileLocation) throws IOException {

    this.configFileLocation = configFileLocation;
    this.properties = new Properties();
    init();
  }

  private void init() throws IOException {

    properties.load(new FileInputStream(this.configFileLocation));

    for (Object key : this.properties.keySet()) {

      String override = System.getProperty((String) key);

      if (override != null) {

        properties.put(key, override);
      }
    }
  }

  public int getIntProperty(String key) {

    return this.properties.contains(key) ? Integer.parseInt(properties.get(key)) : null;
  }

  public String getStringProperty(String key) {

    return (String) this.properties.get(key);
  }
}

.

config.properties

NUMBER_OF_THREADS=100
NUMBER_OF_TASKS=10000
ID_START_RANGE=1
TABLES=TABLE1,TABLE2

NUMBER_OF_THREADS.

java -jar -Dconfig.file.location="C:\\test\\config.properties" -DNUMBER_OF_THREADS=10 Test.jar

'NUMBER_OF_THREADS' int.

new PropertyUtil(System.getProperty("config.file.location")).getIntProperty("NUMBER_OF_THREADS");
+7
Properties properties = new Properties();
properties.load(new FileInputStream("C:\\test\\config.properties"));

, , :

setProperty("NUMBER_OF_THREADS", args[1]);
setProperty("NUMBER_OF_TASKS", args[2]);

config.properties.

0

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