Question

I have the below class which loads database details from a properties file. When the file “dao.properties” is missing the class should throw a DAOConfigurationException but instead I am getting

    javax.servlet.ServletException: Servlet execution threw an exception
root cause

java.lang.ExceptionInInitializerError
    com.clone.dao.DAOFactory.getInstance(DAOFactory.java:19)
    com.clone.controller.register.doPost(register.java:35)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
root cause

com.clone.dao.DAOConfigurationException: Properties file dao.properties not found in classpath.
    com.clone.dao.DAOProperties.<clinit>(DAOProperties.java:15)
    com.clone.dao.DAOFactory.getInstance(DAOFactory.java:19)
    com.clone.controller.register.doPost(register.java:35)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

and in subsequent requests I am getting this exeception

javax.servlet.ServletException: Servlet execution threw an exception
root cause

java.lang.NoClassDefFoundError: Could not initialize class com.clone.dao.DAOProperties
    com.clone.dao.DAOFactory.getInstance(DAOFactory.java:19)
    com.clone.controller.register.doPost(register.java:35)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

This is my code

package com.clone.dao;

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

public class DAOProperties {
    private static final String PROPERTIES_FILE = "dao.properties";
    private static final Properties PROPERTIES = new Properties();
<b> static{
        ClassLoader classloader = Thread.currentThread().getContextClassLoader();
        InputStream propertiesFile = classloader.getResourceAsStream(PROPERTIES_FILE);

        if(propertiesFile==null){
            throw new DAOConfigurationException("Properties file "+PROPERTIES_FILE+" not found in classpath.");
        } 
        try {
            PROPERTIES.load(propertiesFile);
        } catch (IOException e) {
            throw new DAOConfigurationException("Cannot load properties file '"+PROPERTIES_FILE+"'.", e);
        }
    }
</b>
private String specificKey;


    public DAOProperties(String specificKey)
    {
        this.specificKey=specificKey;
    }

    public String getProperty(String key) throws DAOConfigurationException {
        String fullKey = specificKey+"."+key;
        String property = PROPERTIES.getProperty(fullKey);
        if(property==null||property.trim().length()==0){
            throw new DAOConfigurationException("Property '"+fullKey+"' is missing in properties file '"+
                                                        PROPERTIES_FILE+"'.");
        }
        return property;
    }

}

Guys, please explain whats happening this is a lot confusing

Answer 1

It is throwing a DAOConfigurationException:

com.clone.dao.DAOConfigurationException: Properties file dao.properties
     not found in classpath.

However, that’s being wrapped up in an java.lang.ExceptionInInitializerError because your DAOFactory is trying to use DAOProperties. The DAOProperties class can’t be initialized properly because the static initializer fails, and ExceptionInInitializerError is exactly what gets thrown when an static initializer fails.

Perhaps you shouldn’t be doing this within the static initializer?