In this article, we will discuss Properties class – one of the Map implemented classes through Java Hashtable class in detail

1. Key points about Properties:

Properties class is a legacy class
to store key-value pairs,
where both keys & values are of strictly String data-type

2. Properties:

Java Properties class is sub-class of Hashtable class (i.e.; Properties extends Hashtable)
It is used to store key-value pairs where both Key/Value is String type
This is mainly used to store those kinds of data, which changes periodically/frequently like database connection details, etc.
Reason: if we hard-code these things into Java file, then necessary re-compilation & re-package & re-deploy is required (sometime server restart is also required)
Using Java Properties, we can overcome this situation by simply changing values in properties file & re-deploying into server
Java Properties is used to fetch/read environment variables using getProperties() method
Present in java.util package and extends java.util.Hashtable class
Also, implements java.lang.Cloneable, java.io.Serializable marker interfaces (through super class Java Hashtable class) which provides special ability to Java Properties class (provided by JVM at run time) like,
java.lang.Cloneable: to create a duplicate object or to clone an object
java.io.Serializable: to transfer objects across network

Source: Team BenchResources.Net

3. Properties constructors:

3.1 Properties prop = new Properties();

creates an empty Properties object
which has no default values

3.2 Properties prop = new Properties(Properties props);

creates an empty Properties object
with specified default values

4. Java Properties method:

Properties specific methods from Java 1.0 version

Java Properties method	Description
String getProperty(String propKey);	to read/get value associated with the specified property-key returns null, if specified key not in the property list
Object setProperty(String propKey, String propValue);	used to set key-value pair in properties file if key is already present, then value is overridden otherwise, null is returned
Enumeration propertyName();	returns enumeration of keys from property list or to get all properties
void load(InputStream is);	to load properties from (.properties) file to Java properties object
void store(OutputStream os, String comments);	to store/save properties from Java properties object into (.properties) file

5. Properties examples:

5.1 To store or save to properties file

PropertiesStoreInFile.java

package in.bench.resources.java.collection;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Properties;

public class PropertiesStoreInFile {

	public static void main(String[] args) {

		// creating Properties object to store db credentials
		Properties prop = new Properties();

		// writing db credentials as key-value pairs
		prop.setProperty("db.url", "localhost");
		prop.setProperty("db.port", "1521");
		prop.setProperty("db.name", "xe");
		prop.setProperty("db.username", "tiger");
		prop.setProperty("db.password", "scout");

		try {
			// write and save
			OutputStream os = new FileOutputStream("db.properties");
			prop.store(os, "Storing DB Credentials");
			System.out.println("Saved to db.properties file");
		}
		catch (FileNotFoundException fnfex) {
			fnfex.printStackTrace();
		}
		catch (IOException ioex) {
			ioex.printStackTrace();
		}
	}
}

Output:

#Storing DB Credentials
#Fri Aug 26 17:02:08 IST 2016
db.password=scout
db.name=xe
db.username=tiger
db.port=1521
db.url=localhost

5.2 To read from properties file

PropertiesLoadAndReadFromFile.java

package in.bench.resources.java.collection;

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

public class PropertiesLoadAndReadFromFile {

	public static void main(String[] args) {

		// creating Properties object to load/read db credentials
		Properties prop = new Properties();

		try {
			// reading file as stream
			InputStream is = new FileInputStream("db.properties");

			// load db.properties file
			prop.load(is);

			// printing DB credentials values
			System.out.println("Database URL or host : "
					+ prop.getProperty("db.url"));
			System.out.println("Database port : "
					+ prop.getProperty("db.port"));
			System.out.println("Database name : "
					+ prop.getProperty("db.name"));
			System.out.println("Database username : "
					+ prop.getProperty("db.username"));
			System.out.println("Database password : "
					+ prop.getProperty("db.password"));
		}
		catch (FileNotFoundException fnfex) {
			fnfex.printStackTrace();
		}
		catch (IOException ioex) {
			ioex.printStackTrace();
		}
	}
}

Output:

Database URL or host : localhost
Database port : 1521
Database name : xe
Database username : tiger
Database password : scout

References:

Happy Coding !!
Happy Learning !!

BenchResources.Net

Java tutorial for beginners

Java – Properties class with example

1. Key points about Properties:

2. Properties:

3. Properties constructors:

3.1 Properties prop = new Properties();

3.2 Properties prop = new Properties(Properties props);

4. Java Properties method:

5. Properties examples:

5.1 To store or save to properties file

PropertiesStoreInFile.java

Output:

5.2 To read from properties file

PropertiesLoadAndReadFromFile.java

Output:

Related Articles:

References:

Related

1. Key points about Properties:

2. Properties:

3. Properties constructors:

3.1 Properties prop = new Properties();

3.2 Properties prop = new Properties(Properties props);

4. Java Properties method:

5. Properties examples:

5.1 To store or save to properties file

PropertiesStoreInFile.java

Output:

5.2 To read from properties file

PropertiesLoadAndReadFromFile.java

Output:

Related Articles:

References:

Related

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