I have a program which will read everything from config.properties
file if command line does not contain any arguments apart from config.properties file location. Below is my config.properties file-
NUMBER_OF_THREADS: 100
NUMBER_OF_TASKS: 10000
ID_START_RANGE: 1
TABLES: TABLE1,TABLE2
If I am running my program from the command prompt like this-
java -jar Test.jar "C:\\test\\config.properties"
It should read all the four properties from the config.properties
file. But suppose if I am running 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 config.properties file.
Below is my code which is working fine 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 Statement:-
Now what I am trying to do is- Suppose if any person is running program like this
java -jar Test.jar "C:\\test\\config.properties" 10
then in my program, it should overwrite noOfThreads
only-
noOfThreads should be 10 instead of 100
And suppose if that person is running program like this-
java -jar Test.jar "C:\\test\\config.properties" 10 100
then in my program, it should overwrite noOfThreads
and noOfTasks
only-
noOfThreads should be 10 instead of 100
noOfTasks should be 100 instead of 10000
And possible other use cases as well.
Can anyone suggest me how to achieve this scenario? Thanks for the help
And although properties files are simple key=value pairs, there are some corner cases that make it challenging. For example, when setting a key/value pair, the key may be commented out with a hash mark in front of the line.
The syntax to pass properties from command line is as follows, 1 java -D<property1-name>=<property1-value> -D<property2-name>=<property2-value>....... <class-Name> The getProperty () method in System class is used to get the value of a property by specifying the property name as key.
The getProperty () method in System class is used to get the value of a property by specifying the property name as key. view source print? We pass properties subject, score and grade to the above ScoreCardPropertiesTest class as follows, view source print? view source print?
Windows Command Line PowerShell Windows Command Line To run the command, open the command prompt with elevated privilege (run as admin) and run the following command. Replace the Filepathwith the actual file path
When defining command line input as follows
java -jar Test.jar "C:\\test\\config.properties" 10 100
It means one must always provide noOfThreads
to override noOfTasks
.
To solve this you could specify these as system properties on command line along with file location which other wise has a default location too. For example: -
java -jar -Dconfig.file.location="C:\\test\\config.properties" -DNUMBER_OF_THREADS=10 Test.jar
Then.
Properties
.System.getProperty()
.This way no matter how many new properties you introduce your code will always remain same.
You can go step further and encapsulate all of this in a PropertyUtil
that also provide utility methods like getIntProperty()
, getStringProperty()
etc.
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);
}
}
Examples.
config.properties
NUMBER_OF_THREADS=100
NUMBER_OF_TASKS=10000
ID_START_RANGE=1
TABLES=TABLE1,TABLE2
To override NUMBER_OF_THREADS
.
java -jar -Dconfig.file.location="C:\\test\\config.properties" -DNUMBER_OF_THREADS=10 Test.jar
Short hand example to read 'NUMBER_OF_THREADS' as int.
new PropertyUtil(System.getProperty("config.file.location")).getIntProperty("NUMBER_OF_THREADS");
Create a loop, instead.
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's values overridden with the ones provided
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