3.5 spring-replaced-method 子元素的使用与解析
作者:互联网
原文链接:https://my.oschina.net/u/1590001/blog/268212
1.replaced-method 子元素
方法替换: 可以在运行时用新的方法替换现有的方法,与之前的 look-up不同的是replace-method 不但可以动态地替换返回的实体bean,而且可以动态的更改原有方法的逻辑,
1.1.1使用实例:
首先创建一个Bean完成某项业务
1 public class Person {
2
3 public void show() {
4 System.out.println("I am Person ..");
5 }
6 }
在运营一段时间后需要改变原有的逻辑
1 import java.lang.reflect.Method;
2
3 import org.springframework.beans.factory.support.MethodReplacer;
4
5 public class ReplacedClass implements MethodReplacer {
6
7 @Override
8 public Object reimplement(Object obj, Method method, Object[] args) throws Throwable {
9 System.out.println(obj);
10 System.out.println(method.getName());
11 System.out.println("I am replacer...");
12 return null;
13 }
14
15 }
XML 如下
<?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-2.5.xsd">
<bean id="person" class="test.replaced.Person">
<replaced-method name="show" replacer="replace"></replaced-method>
</bean>
<bean id="replace" class="test.replaced.ReplacedClass">
</bean>
</beans>
测试类
1 public class Main {
2
3 public static String XML_PATH = "test\\replaced\\applicationContxt.xml";
4
5 public static void main(String[] args) {
6 try {
7 Resource resource = new ClassPathResource(XML_PATH);
8 XmlBeanFactory beanFactory = new XmlBeanFactory(resource);
9 Person bean = (Person) beanFactory.getBean("person");
10 System.out.println(bean);
11 bean.show();
12 }
13 catch (Exception e) {
14 e.printStackTrace();
15 }
16 }
17 }
好了,运行测试就可以看到我们预期的结果了,控制台成功打印出
test.replaced.Person$$EnhancerBySpringCGLIB$$7f7813f2@1a69b07
test.replaced.Person$$EnhancerBySpringCGLIB$$7f7813f2@1a69b07
show
I am replacer...
知道了这个子元素的用法,我们再来看看Spring是怎么对这个元素进行提取的.
BeanDefinitionParserDelegate.java
1 /**
2 * Parse replaced-method sub-elements of the given bean element.
3 */
4 public void parseReplacedMethodSubElements(Element beanEle, MethodOverrides overrides) {
5 NodeList nl = beanEle.getChildNodes();
6 for (int i = 0; i < nl.getLength(); i++) {
7 Node node = nl.item(i);
8 //仅当在Spring默认Bean的子元素下,
9 //且为<lookup-method 时有效
10 if (isCandidateElement(node) && nodeNameEquals(node, REPLACED_METHOD_ELEMENT)) {
11 Element replacedMethodEle = (Element) node;
12 // 提取要替换的旧的方法
13 String name = replacedMethodEle.getAttribute(NAME_ATTRIBUTE);
14 // 提取对应的新的替换的方法
15 String callback = replacedMethodEle.getAttribute(REPLACER_ATTRIBUTE);
16 ReplaceOverride replaceOverride = new ReplaceOverride(name, callback);
17 // Look for arg-type match elements.
18 List<Element> argTypeEles = DomUtils.getChildElementsByTagName(
19 replacedMethodEle, ARG_TYPE_ELEMENT);
20 for (Element argTypeEle : argTypeEles) {
21 String match = argTypeEle.getAttribute(ARG_TYPE_MATCH_ATTRIBUTE);
22 // 记录参数
23 match = (StringUtils.hasText(match) ? match
24 : DomUtils.getTextValue(argTypeEle));
25 if (StringUtils.hasText(match)) {
26 replaceOverride.addTypeIdentifier(match);
27 }
28 }
29 replaceOverride.setSource(extractSource(replacedMethodEle));
30 overrides.addOverride(replaceOverride);
31 }
32 }
33 }
我们可以看到,无论是lookup-method 还是 replace-method 都是构造了一个methodOverride ,并且最终记录在AbstractBeanDefinition 中的 methodOerrides 属性当中.
而这个属性如何使用,我们后续再继续研究.
转载于:https://my.oschina.net/u/1590001/blog/268212
标签:spring,method,Person,bean,3.5,replaced,public,match 来源: https://blog.csdn.net/cheshifei3571/article/details/100849152