ConfigurationPropertiesClass

Reading and writing configuration for Java application using Properties class

1. Creating a Properties object

• Create a Propertiesobject by using empty constructor:

Properties props = new Properties(); 

• Create a Properties object by supplying a default properties list:

Properties defaultProps = new Properties(); // set default properties
Properties props = new Properties(defaultProps); / create main Properties object

2. Loading properties file

• Load properties from a .properties file using a FileReader object

File configFile = new File("config.properties");
 
FileReader reader = new FileReader(configFile);
 
Properties props = new Properties();
 
props.load(reader); // load the properties file:

• Load properties from a plain text file using an InputStream object:

File configFile = new File("config.properties");

InputStream inputStream = new FileInputStream(configFile);

Properties props = new Properties();
 
props.load(inputStream);

3. Getting properties values

• The Properties class has two methods for retrieving value of a property in the properties file:
• String getProperty(String key): returns value of the property specified by the given key. It returns null if the key not found.
• String getProperty(String key, String defaultValue): like the above method, but this method will return a default value if the key not found.

String host = props.getProperty("host");

4. Setting properties values

• Setting value for a specific property is pretty simple, using this sole method:
• Object setProperty(String key, String value)
• This method returns previous value of the property specified by the given key.

props.setProperty("host", "www.sevdanurgenc.com"); 

5. Saving properties file

• Save to plain text file using a Writerobject:

File configFile = new File("config.properties");
FileWriter writer = new FileWriter(configFile);
props.store(writer, "host settings");