Property initializer addition for PropertyUtilsBean from commons-beanutils

MyPropertyUtilsBean.java

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Map;

import org.apache.commons.beanutils.NestedNullException;
import org.apache.commons.beanutils.PropertyUtils;
import org.apache.commons.beanutils.PropertyUtilsBean;
import org.apache.commons.beanutils.expression.Resolver;
import org.apache.commons.lang.StringUtils;

/**
 * Extension of {@link PropertyUtilsBean} with a method to initialize a bean's members along a path expression.
 */
public class MyPropertyUtilsBean extends PropertyUtilsBean {

	private final static MyPropertyUtilsBean instance = new MyPropertyUtilsBean();

	public static MyPropertyUtilsBean getInstance() {
		return instance;
	}
	
	/** Mostly copy-pasted from {@link PropertyUtilsBean.setProperty}. */
	public void initProperty(Object bean, String path) throws SecurityException, NoSuchMethodException,
			IllegalAccessException, InvocationTargetException {

		if (bean == null) {
			throw new IllegalArgumentException("No bean specified");
		}

		Resolver resolver = getResolver();

		// Iterate through path segments
		while (resolver.hasNested(path)) {
			// Current path segment
			String next = resolver.next(path);

			// Retrieve the bean for this segment, depending on path type
			// TODO add support for non-simple paths
			Object nestedBean = null;
			if (bean instanceof Map) {
				nestedBean = getPropertyOfMapBean((Map) bean, next);
			} else if (resolver.isMapped(next)) {
				nestedBean = getMappedProperty(bean, next);
			} else if (resolver.isIndexed(next)) {
				nestedBean = getIndexedProperty(bean, next);
			} else {
				nestedBean = getSimpleProperty(bean, next);
			}

			// If the component is null, initialize it
			if (nestedBean == null) {

				// There has to be a method get* matching this segment
				String methodName = "get" + StringUtils.capitalize(next);
				Method m = bean.getClass().getMethod(methodName);

				// The return type of this method is the object type we need to init.
				Class<?> propType = m.getReturnType();
				try {
					// Since it's a bean it must have a no-arg public constructor
					Object newInst = propType.newInstance();
					PropertyUtils.setProperty(bean, next, newInst);
					// Now we have something instead of null
					nestedBean = newInst;
				} catch (Exception e) {
					throw new NestedNullException("Could not init property value for '" + path + "' on bean class '"
							+ bean.getClass() + "'. Class: " + propType);
				}
			}

			// Recurse
			bean = nestedBean;
			path = resolver.remove(path);
		}
	}
}

MyPropertyUtilsBeanTest.java

import org.apache.commons.beanutils.NestedNullException;
import org.apache.commons.beanutils.PropertyUtils;
import org.junit.Assert;
import org.junit.Test;

import ch.hotela.casemgmt.util.MyPropertyUtilsBean;

public class MyPropertyUtilsBeanTest {

	@Test
	public void testPath() throws Exception {
		Foo bean = new Foo();
		String path = "foo.foo.foo.bar.value";
		Object value = "Hello world";

		MyPropertyUtilsBean.getInstance().initProperty(bean, path);
		PropertyUtils.setProperty(bean, path, value);

		Object o = PropertyUtils.getProperty(bean, path);
		Assert.assertEquals(value, o);
	}

	@Test(expected = NestedNullException.class)
	public void testPathNoInit() throws Exception {
		Foo bean = new Foo();
		String path = "foo.foo.foo.bar.value";
		Object value = "Hello world";

		// MyPropertyUtilsBean.getInstance().initProperty(bean, path);
		PropertyUtils.setProperty(bean, path, value);

		Object o = PropertyUtils.getProperty(bean, path);
		Assert.assertEquals(value, o);
	}
}

// Beans must be in their own source file !

public class Bar {
	private String value;

	public String getValue() {
		return value;
	}

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

public class Foo {
	private Foo foo;
	private Bar bar;

	public Foo getFoo() {
		return foo;
	}

	public void setFoo(Foo foo) {
		this.foo = foo;
	}

	public Bar getBar() {
		return bar;
	}

	public void setBar(Bar bar) {
		this.bar = bar;
	}
}