思路：根据源码分析，将配置Bean类信息存放到xml文件中，通过解析xml，
然后反射拿到对象 存放到集合中 这里选择hashmap（键放置类名，值放置对象）存放，使用时使用get方法通过键（类名）拿到值（对象）。
后续需要优化的：自动清理缓存垃圾，因为初始化加载把所有的对象都存放进去，造成太多不必要的垃圾对象，导致占用内存，效率低。
1.导入主要工具包 dom4j.jar
2.创建一个javaBean类（注意要添加构造器，因为使用反射）
package com.ms.bean;
/*
*
* Person bean
* **/
public class Person {
private String name;
private int age;
public Person() {
super();
}
public Person(String name, int age) {
super();
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public void info(){
System.out.println("this is a people");
System.out.println("name: "+getName()+" age: "+getAge());
}
}
3.创建一个SpringBeanFactory工厂类
package com.ms.utils;
import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.io.InputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
/**
*
* 模拟spring 加载xml配置文件(dom4j)
*
*/
public class SpringBeanFactory {
//初始化的bean全用map集合保存
public static Map<String,Object> beanMap = new HashMap<String, Object>();
/**
* 解析xml 并且保存到beanmap中
*
*/
public static void parse(String xml){
SAXReader reader = new SAXReader();
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
//从class目录下获取指定的xml
InputStream is = classLoader.getResourceAsStream(xml);
//根节点
Document doc=null;
try {
doc = reader.read(is);
Element rootElement = doc.getRootElement();
Element foo;
//用迭代器遍历bean
for (Iterator i =rootElement.elementIterator("bean");i.hasNext();){
foo = (Element) i.next();
//获取id和class
Attribute id = foo.attribute("id");
Attribute aClass = foo.attribute("class");
//利用反射机制获取Class对象
Class bean = Class.forName(aClass.getText());
//获取class信息
BeanInfo info = Introspector.getBeanInfo(bean);
//获取其属性描述
PropertyDescriptor pd[] = info.getPropertyDescriptors();
//设置方法
Method mSet = null;
//创建一个对象
Object obj = bean.newInstance();
//遍历该bean的property属性
for (Iterator ite = foo.elementIterator("property");ite.hasNext();){
Element foo2 = (Element) ite.next();
//获取name的属性
Attribute name = foo2.attribute("name");
//获取value值
Attribute value = foo2.attribute("value");
for (PropertyDescriptor pp : pd) {
if (pp.getName().equalsIgnoreCase(name.getText())){
mSet = pp.getWriteMethod();
Class<?>[] types = mSet.getParameterTypes();
for (Class<?> type : types) {
if (type.getName().equals("int")){
//转换为整型
mSet.invoke(obj,Integer.parseInt(value.getText()));
}else {
//利用java反射调用set方法
mSet.invoke(obj,value.getText());
}
}
}
}
}
beanMap.put(id.getText(),obj);
}
} catch (DocumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NumberFormatException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IntrospectionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
4.创建一个mySpringBean.xml 放置在src目录下面
<?xml version="1.0" encoding="UTF-8"?>
<beans>
<bean id="person" class="com.ms.bean.Person">
<property name="name" value="jack"/>
<property name="age" value="20"/>
</bean>
</beans>
5.创建测试类
package test;
import org.junit.Test;
import com.ms.bean.Person;
import com.ms.dao.IString;
import com.ms.dao.myString;
import com.ms.utils.SpringBeanFactory;
/**
* this is a test
*
* */
public class test {
public test() {
SpringBeanFactory.parse("myStringBean.xml");
}
@Test
public void testPerson(){
Person person = (Person)SpringBeanFactory.beanMap.get("person");
person.info();
}
}
6.输出结果如图所示