1.手写LcSpring（1）-优快云博客

本文链接：https://blog.youkuaiyun.com/zlc819240815/article/details/80704890

本文介绍了一种使用XML文件来配置并利用Java反射机制实现对象实例化的方法。通过具体的代码示例，展示了如何从XML文件中读取配置信息，并根据这些信息创建指定类的对象。同时，该文还涉及了如何设置对象属性的过程。

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xml文件

</LcSpring>

xml解析核心类

package com.java.zlc;

import java.io.File;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.*;

import com.java.zlc.Teacher;

public class LcSpring {
   //单个对象注入
   public static void main(String[] args) {
       LcSpring lcSpring=new LcSpring();
       Student student=(Student) lcSpring.getBean("s1");
       System.out.println(student);

       Teacher teacher=(Teacher) lcSpring.getBean("t1");
       System.out.println(teacher);
   }

   public Object getBean(String id) {
       String classname = "";
       Object object = null;
       Map map = new HashMap();
       try {
           File inputFile = new File("LcSpring.xml");
           // 1.create DocumentBuilder object
           DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
           DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
           // 2.create Document object
           Document doc = dBuilder.parse(inputFile);
           doc.getDocumentElement().normalize();
           // get root node
           // Node node=doc.getFirstChild();
           String nameString = doc.getFirstChild().getNodeName();
           if (!nameString.equals("LcSpring")) {
               throw new Exception("未发现LcSpring");
           }
           Node node = doc.getElementsByTagName(id).item(0);
           classname = ((Element) node).getAttribute("classname");
           // 3.get student list;
           String[] classtr = classname.split("\\.");
           String myclass = classtr[classtr.length - 1];
           NodeList nList = doc.getElementsByTagName(myclass);

for (int temp = 0; temp < nList.getLength(); temp++) {
Node nNode = nList.item(temp);

               if (nNode.getNodeType() == Node.ELEMENT_NODE) {
                   Element eElement = (Element) nNode;
                   NodeList nodeList = eElement.getElementsByTagName("property");
                   for (int i = 0; i < nodeList.getLength(); i++) {

                       String value = nodeList.item(i).getTextContent();
                       String property = ((Element) nodeList.item(i)).getAttribute("name");
                       map.put(property, value);
                   }
               }
           }
       } catch (Exception e) {
           e.printStackTrace();
       }
       try {
           object = Class.forName(classname).getConstructor().newInstance();
           object = setValue(object, map);
       } catch (Exception e) {
           e.printStackTrace();
       }
       return object;
   }

   public Object setValue(Object object, Map map) {
       try {
           for (Object key : map.keySet()) {
               String value = (String) map.get(key);
               Field f1 = object.getClass().getDeclaredField((String) key);
               f1.setAccessible(true);
               String type = f1.getType().toString();// 得到此属性的类型
               if (type.endsWith("int") || type.endsWith("Integer")) {
                   f1.set(object, Integer.parseInt(value));
               } else {
                   f1.set(object, value);
               }
           }
       } catch (Exception e) {
           e.printStackTrace();
       }
       return object;
   }
}

实体类

package com.java.zlc;

public class Student {

private int rollno;
private String firstname;
private String marks;
@Override
public String toString() {
return "Student [rollno=" + rollno + ", firstname=" + firstname
+ ", marks=" + marks + "]";
}

}