通過以上幾篇文章,已經知道反射是什麼,大概是怎麼用,接下來用反射做一個簡單的實例模擬框架運行原理
配置文件config.xml的代碼如下
<?xml version="1.0" encoding="UTF-8"?>
<beans>
<bean id="javaBean" class="javatribe.fts.reflection.JavaBean">
<property name="userName">
<value>馮先生</value>
</property>
<property name="password">
<value>88888888</value>
</property>
</bean>
</beans>
然後建立一個JavaBean
package javatribe.fts.reflection;
public class JavaBean {
private String userName;
private String password;
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
接下來建立一個BeanFactory這是bean工廠,學習過Spring框架大體都會有所瞭解的了
package javatribe.fts.reflection;
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工廠的初始化.
* @param xml xml配置文件
*/
public void init(String xml) {
try {
//讀取指定的配置文件
SAXReader reader = new SAXReader();
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
//從class目錄下獲取指定的xml文件
InputStream ins = classLoader.getResourceAsStream(xml);
Document doc = reader.read(ins);
Element root = doc.getRootElement();
Element foo;
//遍歷bean
for (Iterator i = root.elementIterator("bean"); i.hasNext();) {
foo = (Element) i.next();
//獲取bean的屬性id和class
Attribute id = foo.attribute("id");
Attribute cls = foo.attribute("class");
//利用Java反射機制,通過class的名稱獲取Class對象
Class bean = Class.forName(cls.getText());
//獲取對應class的信息
java.beans.BeanInfo info = java.beans.Introspector.getBeanInfo(bean);
//獲取其屬性描述
java.beans.PropertyDescriptor pd[] = info.getPropertyDescriptors();
//設置值的方法
Method mSet = null;
//創建一個對象
Object obj = bean.newInstance();
//遍歷該bean的property屬性
for (Iterator ite = foo.elementIterator("property"); ite.hasNext();) {
Element foo2 = (Element) ite.next();
//獲取該property的name屬性
Attribute name = foo2.attribute("name");
String value = null;
//獲取該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;
}
for (int k = 0; k < pd.length; k++) {
if (pd[k].getName().equalsIgnoreCase(name.getText())) {
mSet = pd[k].getWriteMethod();
//利用Java的反射極致調用對象的某個set方法,並將值設置進去
mSet.invoke(obj, value);
}
}
}
//將對象放入beanMap中,其中key爲id值,value爲對象
beanMap.put(id.getText(), obj);
}
} catch (Exception e) {
System.out.println(e.toString());
}
}
/**
* 通過bean的id獲取bean的對象.
* @param beanName bean的id
* @return 返回對應對象
*/
public Object getBean(String beanName) {
Object obj = beanMap.get(beanName);
return obj;
}
/**
* 測試方法.
* @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());
}
}
最後輸出結果是
userName=馮先生
password=888888