java 通过配置文件获取对应的值

当我们有的时候觉得在java程序中添加参数值的时候觉得需要改变代码麻烦，如果你像尝试通过配置文件添加对应的值，而不用去改变*.java文件时，一个小程序。


直接看代码

<?xml version="1.0" encoding = "UTF-8" ?>
<listeners>
	<listener class="com.test.TestElement"></listener>
	
</listeners>

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

public class Utils {
	private static List<Object> listeners = new ArrayList<Object>();

	static {
		SAXReader sax = new SAXReader();
		Document doc = null;
		try {
			doc = sax.read(Utils.class.getClassLoader()
					.getResourceAsStream("listeners.xml"));
			Element root = doc.getRootElement();
			List list = root.elements("listener");
			for (int i = 0; i < list.size(); i++) {
				Element element = (Element) list.get(i);
				String clazz = element.attributeValue("class");
				Object o = Class.forName(clazz).newInstance();
				listeners.add(o);
			}
		} catch (DocumentException e) {
			e.printStackTrace();
		} catch (InstantiationException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
	
	public static List<Object>  getListeners() {
		return listeners;
	}
}

如果对应配置文件中还有别的属性的时候，可以参看下面的代码：

<beans>
	<bean id="a" class="com.A" />
	<bean id="b" class="com.B" >
		<property name="b_a" bean="a"/>
	</bean>
	
</beans>

import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.jdom.Document;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;

public class READ{
	
	private Map<String , Object> beans = new HashMap<String, Object>();
	
	
	public ClassPathXmlApplicationContext() throws Exception {
		SAXBuilder sb=new SAXBuilder();
	    
	    Document doc=sb.build(this.getClass().getClassLoader().getResourceAsStream("beans.xml"));
	    Element root=doc.getRootElement(); 
	    List list=root.getChildren("bean");
	    for(int i=0;i<list.size();i++){
	       Element element=(Element)list.get(i);
	       String id=element.getAttributeValue("id");
	       String clazz=element.getAttributeValue("class");
	       Object o = Class.forName(clazz).newInstance();
	       beans.put(id, o);
	       
	       for(Element propertyElement : (List<Element>)element.getChildren("property")) {
	    	   String name = propertyElement.getAttributeValue("name");
	    	   String bean = propertyElement.getAttributeValue("bean");
	    	   Object beanObject = beans.get(bean);
	    	   
	    	   String methodName = "set" + name.substring(0, 1).toUpperCase() + name.substring(1);
	    	   
	    	   Method m = o.getClass().getMethod(methodName, beanObject.getClass().getInterfaces());
	    	   m.invoke(o, beanObject);
	       }
	    }  
	  
	}



	public Object getBean(String id) {
		return beans.get(id);
	}

}