JavaBeans comparison

Does anyone know a free open source library (utility class) that allows you to compare two instances of a java bean and return a list / array of properties. The values in the two instances are different? Please post a small sample

Cheers, Thomas

Solution

The bean comparator of Apache Commons is what you are looking for

to update. A simple example of comparing JavaBeans with an attribute (the comparison will only produce one attribute, and you should create as many bean comparators as the attributes to match)

import org.apache.commons.beanutils.BeanComparator;

public class TestBeanComparator
{
    public TestBeanComparator()
    {
    }

    public class TestBean
    {
        int value;

        public TestBean()
        {
        }

        public int getValue()
        {
            return value;
        }

        public void setValue(int value)
        {
            this.value = value;
        }
    }

    public static void main(String[] args)
    {
        TestBeanComparator tbc = new TestBeanComparator();

        tbc.go();
    }

    public void go()
    {
        TestBean tbs [] = new TestBean[10];

        for (int i = 0; i < tbs.length; i++)
        {
            tbs[i] = new TestBeanComparator.TestBean();
            tbs[i].setValue((int) (Math.random() * 10));

            System.out.println("TestBean["+i+"] = " + tbs[i].getValue());
        }

        BeanComparator bc = new BeanComparator("value");

        System.out.println("");
        System.out.println("Value to match: " + tbs[0].getValue());
        for (int i = 1; i < tbs.length; i++)
        {
            if(bc.compare(tbs[i],tbs[0]) == 0)
            {
               System.out.println("Match found in bean "+ i); 
            }
        }
    }
}

After some tests, one result is successful This is the output:

TestBean[0] = 0
TestBean[1] = 4
TestBean[2] = 0
TestBean[3] = 2
TestBean[4] = 7
TestBean[5] = 3
TestBean[6] = 0
TestBean[7] = 3
TestBean[8] = 7
TestBean[9] = 3

Value to match: 0
Match found in bean 2
Match found in bean 6

Obviously, increasing the size of the testbean array will increase the chance of obtaining a match

You need to import the following jar into the project: commons - logging - version jar,commons-beanutils-version. jar,commons-beanutils-core-version. jar,commons-beanutils-bean-collections-version. jar,commons -collections-version. jar.

These files are contained in the Commons logging, commons bean utils, and Commons collections APIs