基于JAVA反射的Spring原理----例子

<span style="font-size:14px;"></span><pre name="code" class="java">package com.lhh.bean;

public class JavaBean {

private String username;
private String password;

public String getPassword() {
return password;
}

public String getUserName() {
return username;
}

public void setUserName(String userName) {
this.username = userName;
}

public void setPassword(String password) {
this.password = password;
}
}

<span style="font-size:14px;">package com.lhh.factory;

import java.io.InputStream;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

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

public class BeanFactory {

private Map<String, Object> beanMap = new HashMap<String, Object>();

/**
* bean工厂的初始化.
*
* @param xml xml配置文件
*/
public void init(String xml) {
try {
//1.创建读取配置文件的reader对象
SAXReader reader = new SAXReader();

//2.获取当前线程中的类装载器对象
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();

//3.从class目录下获取指定的xml文件
InputStream ips = classLoader.getResourceAsStream(xml);
Document doc = reader.read(ips);
Element root = doc.getRootElement();
Element foo;

//4.遍历xml文件当中的Bean实例
for (Iterator i = root.elementIterator("bean"); i.hasNext();) {
foo = (Element) i.next();

//5.针对每个一个Bean实例，获取bean的属性id和class
Attribute id = foo.attribute("id");
Attribute cls = foo.attribute("class");

//6.利用Java反射机制，通过class的名称获取Class对象
Class bean = Class.forName(cls.getText());
//7.获取对应class的信息
java.beans.BeanInfo info = java.beans.Introspector.getBeanInfo(bean);
//8.获取其属性描述
java.beans.PropertyDescriptor pd[] = info.getPropertyDescriptors();

//9.创建一个对象，并在接下来的代码中为对象的属性赋值
Object obj = bean.newInstance();

//10.遍历该bean的property属性
for (Iterator ite = foo.elementIterator("property"); ite.hasNext();) {
Element foo2 = (Element) ite.next();

//11.获取该property的name属性
Attribute name = foo2.attribute("name");
String value = null;

//12.获取该property的子元素value的值
for (Iterator ite1 = foo2.elementIterator("value"); ite1.hasNext();)
{
Element node = (Element) ite1.next();
value = node.getText();
break;
}

//13.利用Java的反射机制调用对象的某个set方法，并将值设置进去
for (int k = 0; k < pd.length; k++) {
if (pd[k].getName().equalsIgnoreCase(name.getText()))
{
Method mSet = null;
mSet = pd[k].getWriteMethod();
mSet.invoke(obj, value);
}
}
}

//14.将对象放入beanMap中，其中key为id值，value为对象
beanMap.put(id.getText(), obj);
}
} catch (Exception e) {
System.out.println(e.toString());
}
}

/**
* 通过bean的id获取bean的对象.
*
* @param beanName
*            bean的id
* @return 返回对应对象
*/
public Object getBean(String beanName) {
Object obj = beanMap.get(beanName);
return obj;
}

}
</span>

package com.lhh.test;

import com.lhh.bean.JavaBean;
import com.lhh.factory.BeanFactory;

public class test {

/**
* 测试方法.
*
* @param args
*/
public static void main(String[] args) {
BeanFactory factory = new BeanFactory();
factory.init("config.xml");
JavaBean javaBean = (JavaBean) factory.getBean("javaBean");
System.out.println("userName = " + javaBean.getUserName());
System.out.println("password = " + javaBean.getPassword());
}

}

XML配置文件config.xml

<?xml version="1.0" encoding="UTF-8"?>

<beans>
<bean id="javaBean" class="com.lhh.bean.JavaBean">
<property name="userName">
<value>老辉辉</value>
</property>
<property name="password">
<value>hunteroman</value>
</property>
</bean>
</beans>