利用dom4j.jar自制实例化Spring容器

首先在项目中导入dom4j,jar包

一、对于已有的配置文件xml和需实现类PersonServiceBean.java

package cn.itcast.service.impl;
import cn.itcast.service.PersonService;
public class PersonServiceBean implements PersonService {
public void save(){
System.out.println("i am save()");
}
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
 
<bean id="personService" class="cn.itcast.service.impl.PersonServiceBean"></bean>
</beans>

二、利用BeanDefinition.java存储xml中的文件

package junit.test;
public class BeanDefinition {
private String id;
private String className;
public BeanDefinition(String id, String className) {
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;
}
}

利用DanChengClassPathXMLApplicationContext.java文件进行实例化操作

package junit.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.Element;
import org.dom4j.XPath;
import org.dom4j.io.SAXReader;
/**
* 自制实例化Spring容器
* @author Administrator
*
*/
public class DanChengClassPathXMLApplicationContext {
private List<BeanDefinition> beanDefines = new ArrayList<BeanDefinition>();
private Map<String, Object> sigletons = new HashMap<String, Object>();
public DanChengClassPathXMLApplicationContext(String filename){
this.readXML(filename);
this.instanceBean();
}
/**
* 完成bean的实例化
*/
private void instanceBean() {
for(BeanDefinition beanDefinition : beanDefines){
try {
if(beanDefinition.getClassName() != null && !"".equals(beanDefinition.getClassName().trim()))
sigletons.put(beanDefinition.getId(), Class.forName(beanDefinition.getClassName()).newInstance());
} catch (Exception e) {
e.printStackTrace();
}
}
}
/**
* 读取配置文件
* @param filename
*/
private void readXML(String filename) {
SAXReader saxReader = new SAXReader();
//创建一个读取器
Document document = null;
try{
URL xmlpath = this.getClass().getClassLoader().getResource(filename);
document = saxReader.read(xmlpath);
//读取文件内容
Map<String, String> nsMap = new HashMap<String, String>();
nsMap.put("ns", "http://www.springframework.org/schema/beans");
//加入命名空间
XPath xsub = document.createXPath("//ns:beans/ns:bean");//创建beans/bean查询路径
xsub.setNamespaceURIs(nsMap);//设置命名空间
List<Element> beans = xsub.selectNodes(document);
for(Element element : beans){
String id = element.attributeValue("id");
String clazz = element.attributeValue("class");
BeanDefinition beanDefine = new BeanDefinition(id, clazz);
beanDefines.add(beanDefine);
}
} catch (Exception e){
e.printStackTrace();
}
}
/**
* 获取bean实例
* @param beanName
* @return
*/
public Object getBean(String beanName){
return this.sigletons.get(beanName);
}
}

package junit.test;
import org.junit.BeforeClass;
import org.junit.Test;
import cn.itcast.service.PersonService;
public class SpringTest {
@BeforeClass
public static void setUpBeforeClass() throws Exception {
}
@Test
public void instanceSpring() {
DanChengClassPathXMLApplicationContext ctx = new DanChengClassPathXMLApplicationContext("beans.xml");
PersonService personService = (PersonService)ctx.getBean("personService");
personService.save();
}
}

最后

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