CODEWITHSUNDEEP
java
Arian
Arian

Reputation: 7719

Initialize variable with value stored in an external file

I have an Email class which is abstract. It has several children: AuthenticationEmail, MarketingEmail, etc. I want to initialize value of a field (which is final static) with a string stored in an external file.

At first I though I could use Spring's @Value but it turned out that the class needs to be a component. Then I tried the following code (static initialization and etc.): 

public abstract class UserAccountAuthenticationEmail extends Email implements Serializable {    
    @Value("${email.address.from.authentication}")
    private final static String SENDER_EMAIL_ADDRESS;

    static {

        Properties prop = new Properties();
        String propFileName = "config.properties";
        InputStream inputStream;
        if (inputStream != null) {
            prop.load(inputStream);
            inputStream = getClass().getClassLoader().getResourceAsStream(propFileName);

        } else {
            throw new FileNotFoundException("property file '" + propFileName + "' not found in the classpath");
        }
    }

    @Override
    public String getSender() {
        return SENDER_EMAIL_ADDRESS;
    }
}

It doesn't work either, as getClass is a non-static method and cannot be instantiated inside the static block.

How can I initialize the value of this variable from a file? and preferably only one time. Is there any standard method to do that? something like @Value, instead of manually reading from IO?

Upvotes: 0

Views: 434

Answers (2)

Arian
Arian

Reputation: 7719

Fixed it this way:

private final static String DEFAULT_SENDER_EMAIL_ADDRESS;

static {
    String value = "";
    try {
        Properties prop = new Properties();
        String propFileName = "application.properties";
        InputStream inputStream = ClassLoader.getSystemClassLoader().getResourceAsStream(propFileName);
        if (inputStream != null) {
            prop.load(inputStream);
           value = prop.getProperty("email.authentication.sender");
        }

    }
    catch (Exception e){
        e.printStackTrace();
    }
    DEFAULT_SENDER_EMAIL_ADDRESS = value;
}

public String getSender() {
    return DEFAULT_SENDER_EMAIL_ADDRESS;
}

Upvotes: 0

Manikandan Saravanan
Manikandan Saravanan

Reputation: 11

Hope it can help you. A static final variable can't be changed after the first initialization.

public  class UserAccountAuthenticationEmail  implements Serializable {

private final static String SENDER_EMAIL_ADDRESS =getVal();
public static String getVal() {

    try {
        Properties prop = new Properties();
        String propFileName = "C:\\SMS\\config.properties";
        InputStream inputStream;
        inputStream = new FileInputStream(propFileName);
        if (inputStream != null) {
            prop.load(inputStream);
           return prop.getProperty("email");
        } else {
            throw new FileNotFoundException("property file '" + propFileName + "' not found in the classpath");
        }
    }
    catch (Exception e){
        e.printStackTrace();
    }
    return "";
}

public static void main(String[] args) {
    System.out.println(SENDER_EMAIL_ADDRESS);
  }
}

Upvotes: 1

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