What's Going On in There? Java Reflection for Program Insight

May 12, 2009
By Sridhar M S

Using Reflection to Execute Class Methods at Runtime

Suppose you have a class and want to use it at runtime. The code below shows how you can load the class and execute a desired method at runtime. The assumption here is that the method's name is setProperties and it takes an argument of type java.util.Properties.

Class newClass = null;
 
Method getInstanceMethod = null;
 
Properties prop = new Properties();
prop.put("argName", "argValue");
try
{
    Object obj = newClass.newInstance();
    getInstanceMethod = newClass.getMethod("setProperties", 
        new Class[]{new Properties().getClass()});
 
}
catch (Exception ex)
{
    //Exception in loading Class:" + ex.getMessage();
}

These utilities allow an IDE developer to accommodate Java as a supported programming language quite easily.

A Word of Caution

You have seen the advantages of using the Java Reflection API, but you must understand the disadvantages of reflection as well. For example, debugging will be a nightmare if you don't understand the process well. It is best to use reflection to solve a given problem only when you have weighed it against other available mechanisms.

Code Download

Reflection_src

For Further Reading

"Using Java Reflection" (from Sun Developer Network)

"Trail: The Reflection API" (from Sun Developer Network)

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