Spring 中仿照ClassPathXMLApplicationContext类生产类加载容器

最新推荐文章于 2025-09-06 16:35:37 发布

原创最新推荐文章于 2025-09-06 16:35:37 发布 · 514 阅读

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#spring #ClassPathXMLApplicat

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本文介绍如何使用Dom4j库解析XML文件并从中获取对象实例，通过MyApplication类读取XML配置信息并实例化指定的类对象。

MyApplication.java和Mybeans.java代替ClassPathXMLApplicationContext类

实现如下：

MyApplication.java

package com.test;

import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

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


public class MyApplication {
	//保存XML文件中解析出来的user对象，保存ID和类名
	private List<Mybeans> beanList = new ArrayList<Mybeans>();
	//保存所有bean中所映射的类对象
	private Map<String, Object> beans = new HashMap<String, Object>();
	
	public MyApplication(String xmlFileName){
		readXml(xmlFileName);
		instanceObject();
	}

	private void instanceObject() {
		for(Mybeans bean : beanList){
			String key = bean.getId();
			Object obj = null;
			try {
				obj = Class.forName(bean.getClassName()).newInstance();
			} catch (InstantiationException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IllegalAccessException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (ClassNotFoundException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			beans.put(key, obj);
		}
	}

	private void readXml(String xmlFileName) {
		SAXReader saxReader = new SAXReader();
		Document document = null;
		URL xmlPath = this.getClass().getClassLoader().getResource(xmlFileName);
		try {
			document = saxReader.read(xmlPath);
		} catch (DocumentException e) {
			e.printStackTrace();
		}
		Map<String, String> nsMap = new HashMap<String, String>();
		nsMap.put("ns", "http://www.springframework.org/schema/beans");
		XPath xsub = document.createXPath("//ns:beans/ns:bean");//创建beans/bean查询路径
		xsub.setNamespaceURIs(nsMap);
		List<Element> beans = xsub.selectNodes(document);
		for (Element element : beans) {
			String id = element.attributeValue("id");
			String clazz = element.attributeValue("class");
			Mybeans bean = new Mybeans(id,clazz);
			beanList.add(bean);
		}
	}
	
	public Object getBean(String id) {
		if(beans.containsKey(id)){
			return beans.get(id);
		}
		return null;
	}
	

}

Mybeans.java

package com.test;

public class Mybeans {
	private String id;
	private String className;

	public Mybeans(String id, String className) {
		super();
		this.id = id;
		this.className = className;
	}

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getClassName() {
		return className;
	}

	public void setClassName(String className) {
		this.className = className;
	}

}

需要的jar包，除了spring的core包外还需要如下包：dom4j-1.6.jar和lib下的所有包下载地址： http://download.youkuaiyun.com/detail/u010426133/7763815