java中itcast_ITCAST视频-Spring学习笔记（编码剖析@Resource注解的实现原理）

感谢ITCAST发布的免费视频。

packagejunit.test;

importjava.lang.annotation.ElementType;

importjava.lang.annotation.Retention;

importjava.lang.annotation.RetentionPolicy;

importjava.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)

@Target({ElementType.FIELD, ElementType.METHOD})

public@interfaceMyResource{

publicString name()default"";

}

packagejunit.test;

importjava.beans.IntrospectionException;

importjava.beans.Introspector;

importjava.beans.PropertyDescriptor;

importjava.lang.reflect.Field;

importjava.lang.reflect.InvocationTargetException;

importjava.lang.reflect.Method;

importjava.net.URL;

importjava.util.ArrayList;

importjava.util.HashMap;

importjava.util.List;

importjava.util.Map;

importorg.apache.commons.beanutils.ConvertUtils;

importorg.dom4j.Document;

importorg.dom4j.Element;

importorg.dom4j.XPath;

importorg.dom4j.io.SAXReader;

publicclassMyClassPathXMLApplicationContext {

privateListbeanDefines=newArrayList();

privateMapsigletons=newHashMap();

publicMyClassPathXMLApplicationContext(String fileName) {

this.readXML(fileName);

this.instanceBeans();

this.annotationInject();

this.injectObject();

}

privatevoidannotationInject() {

//TODOAuto-generated method stub

for(String beanName :sigletons.keySet()) {

Object bean =sigletons.get(beanName);

if(bean !=null) {

try{

PropertyDescriptor[] ps = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();

for(PropertyDescriptor properdesc : ps) {

Method setter = properdesc.getWriteMethod();

if(setter !=null&& setter.isAnnotationPresent(MyResource.class)) {

MyResourceresource = setter.getAnnotation(MyResource.class);

Object value =null;

if(resource.name() !=null&& !resource.name().equals("")) {

String name = resource.name();

value =sigletons.get(name);

}else{

value =sigletons.get(properdesc.getName());

if(value ==null) {

for(String key :sigletons.keySet()) {

if(properdesc.getPropertyType().isAssignableFrom(sigletons.get(key).getClass())) {

value =sigletons.get(key);

break;

}

}

}

}

setter.setAccessible(true);

setter.invoke(bean, value);

}

}

Field[] fields = bean.getClass().getDeclaredFields();

for(Field field : fields) {

if(field.isAnnotationPresent(MyResource.class)) {

MyResourceresource = field.getAnnotation(MyResource.class);

Object value =null;

if(resource.name() !=null&& !resource.name().equals("")) {

String name = resource.name();

value =sigletons.get(name);

}else{

value =sigletons.get(field.getName());

if(value ==null) {

for(String key :sigletons.keySet()) {

if(field.getType().isAssignableFrom(sigletons.get(key).getClass())) {

value =sigletons.get(key);

break;

}

}

}

}

field.setAccessible(true);

field.set(bean, value);

}

}

}catch(IntrospectionException e) {

//TODOAuto-generated catch block

e.printStackTrace();

}catch(IllegalArgumentException e) {

//TODOAuto-generated catch block

e.printStackTrace();

}catch(IllegalAccessException e) {

//TODOAuto-generated catch block

e.printStackTrace();

}catch(InvocationTargetException e) {

//TODOAuto-generated catch block

e.printStackTrace();

}

}

}

}

privatevoidinjectObject() {

//TODOAuto-generated method stub

for(BeanDefinition beanDefinition :beanDefines) {

Object bean =sigletons.get(beanDefinition.getId());

if(bean !=null) {

try{

PropertyDescriptor[] ps = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();

for(PropertyDefinition properties : beanDefinition.getProperties()) {

for(PropertyDescriptor properDesc : ps) {

if(properties.getName().equals(properDesc.getName())) {

Method setter = properDesc.getWriteMethod();//get the setter method

if(setter !=null) {

Object value =null;

if(properties.getRef() !=null&& !properties.getRef().equals("")) {

value =sigletons.get(properties.getRef());

}else{

value = ConvertUtils.convert(properties.getValue(), properDesc.getPropertyType());

}

setter.setAccessible(true);

setter.invoke(bean, value);//set ref object to the property

}

break;

}

}

}

}catch(Exception e) {

//TODOAuto-generated catch block

e.printStackTrace();

}

}

}

//List properties =

}

privatevoidinstanceBeans() {

//TODOAuto-generated method stub

for(BeanDefinition beanDefinition :beanDefines) {

try{

if(beanDefinition.getClassName() !=null&& !beanDefinition.getClassName().equals("")) {

sigletons.put(beanDefinition.getId(), Class.forName(beanDefinition.getClassName()).newInstance());

}

}catch(Exception e) {

e.printStackTrace();

}

}

}

privatevoidreadXML(String fileName) {

//TODOAuto-generated method stub

SAXReader saxReader =newSAXReader();

Document document =null;

try{

URL xmlpath =this.getClass().getClassLoader().getResource(fileName);

Map nsMap =newHashMap();

XPath xsub =null;

List beans =null;

document = saxReader.read(xmlpath);

nsMap.put("ns","http://www.springframework.org/schema/beans");//add namespace

xsub = document.createXPath("//ns:beans/ns:bean");//create beans/bean query path

xsub.setNamespaceURIs(nsMap);//set namespace

beans = xsub.selectNodes(document);//get nodes of the document

for(Element element : beans) {

String id = element.attributeValue("id");

String clazz = element.attributeValue("class");

BeanDefinition beanDefine =newBeanDefinition(id, clazz);

XPath propertySub = element.createXPath("ns:property");

List properties =null;

propertySub.setNamespaceURIs(nsMap);

properties = propertySub.selectNodes(element);

for(Element property : properties) {

String propertyName = property.attributeValue("name");

String propertyRef = property.attributeValue("ref");

String propertyValue = property.attributeValue("value");

PropertyDefinition pro =newPropertyDefinition();

pro.setName(propertyName);

pro.setRef(propertyRef);

pro.setValue(propertyValue);

beanDefine.getProperties().add(pro);

}

beanDefines.add(beanDefine);

}

}catch(Exception e) {

e.printStackTrace();

}

}

publicObject getBean(String beanName) {

returnthis.sigletons.get(beanName);

}

}