一个用于seam单元测试的DI(依赖注入)工具类

package com.yerk.seam;

import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;

import org.jboss.seam.annotations.In;

public final class ComponentContexts {

	private final Map<String, Object> componentMap = new HashMap<String, Object>();

	private ComponentContexts() {
	}

	private static ComponentContexts instance = new ComponentContexts();

	final public static ComponentContexts getInstance() {
		return instance;
	}

	public void injectObject(Object component) throws Exception {
		if (component == null) {
			throw new RuntimeException("Null Object Cann't be Injected!");
		}

		for (Field field : component.getClass().getDeclaredFields()) {
			if (field.isAnnotationPresent(In.class)) {
				injectObjectToField(component, field);
			}
		}
	}

	private void injectObjectToField(Object obj, Field field) throws Exception {
		Object component = componentMap.get(field.getName());
		
		if (component == null) {
			component = createComponent(field);
			componentMap.put(field.getName(), component);
		}
		
		field.setAccessible(true);
		field.set(obj, component);
		injectObject(component);
	}

	private Object createComponent(Field field) throws Exception {
		Class<?> clazz = field.getType();
		String classFullName = clazz.getName();
		
		if (clazz.isInterface()) {
			classFullName = new StringBuilder().append(
					clazz.getPackage().getName()).append(".impl.").append(
					clazz.getSimpleName()).append("Impl").toString();
		}
		
		return Class.forName(classFullName).newInstance();
	}

}