使用dom4j:读取spring配置文件,实例化bean对象并注入依赖对象
案例:
先加入dom4j的jar包。
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BlogClassPathXMLApplicationContext.java
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package junit.test; import java.beans.Introspector; import java.beans.PropertyDescriptor; import java.lang.reflect.Field; import java.lang.reflect.Method; import java.net.URL; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import org.apache.commons.beanutils.ConvertUtils; import org.dom4j.Document; import org.dom4j.Element; import org.dom4j.XPath; import org.dom4j.io.SAXReader; public class BlogClassPathXMLApplicationContext { private List<BeanDefinition> beanDefines = new ArrayList<BeanDefinition>(); private Map<String, Object> sigletons = new HashMap<String, Object>(); public BlogClassPathXMLApplicationContext(String filename){ readXML(filename); instanceBeans(); annotationInjection(); injectObject(); } private void annotationInjection() { for (BeanDefinition beanDefinition : beanDefines) { Object bean = sigletons.get(beanDefinition.getId()); if (bean != null) { try { BlogResource resource = null; Object value = null; //按属性注解 PropertyDescriptor[] propertyDescriptors = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();//得到beanDefinition对应的类的所有属性 for (PropertyDescriptor propertyDescriptor : propertyDescriptors) { Method setter = propertyDescriptor.getWriteMethod();//得到属性的settter方法 if (setter != null && setter.isAnnotationPresent(BlogResource.class)) { resource = setter.getAnnotation(BlogResource.class); if (resource.name() != null && !"".equals(resource.name())) {//查找顺序1:注解有name,严格按name指定的查找 value = sigletons.get(resource.name()); }else { value = sigletons.get(propertyDescriptor.getName());//查找顺序2:注解没有name,默认按字段名称查找 if (value == null) {//查找顺序3:注解没有name,默认按字段名称查找不到,则按类型查找 for (String key : sigletons.keySet()) { if (propertyDescriptor.getPropertyType().isAssignableFrom(sigletons.get(key).getClass())) { value = sigletons.get(key); break; } } } } setter.setAccessible(true); setter.invoke(bean, value); } } //按字段注解 Field[] fileds = bean.getClass().getDeclaredFields(); for (Field field : fileds) { resource = field.getAnnotation(BlogResource.class);//得到字段的注解 if (resource != null) { if (resource.name() != null && !"".equals(resource.name())) { value = sigletons.get(resource.name()); }else { 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 (Exception e) { e.printStackTrace(); } } } } /** * 为属性注入值 */ private void injectObject() { for (BeanDefinition beanDefinition : beanDefines) { Object bean = sigletons.get(beanDefinition.getId()); if (bean != null) { try { PropertyDescriptor[] propertyDescriptors = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();//得到beanDefinition对应的类的所有属性 for (PropertyDescriptor propertyDescriptor : propertyDescriptors) { for (PropertyDefiniton propertyDefiniton : beanDefinition.getProperties()) {//得到beans.xml中bean的所有property if (propertyDescriptor.getName().equals(propertyDefiniton.getName())) {//比较beanDefinition中定义的属性与beans.xml中<bean/>节点下的property元素的name是否相同 Method setter = propertyDescriptor.getWriteMethod(); if (setter != null) { Object arg = null; if (propertyDefiniton.getRef() != null && !"".equals(propertyDefiniton.getRef())) { arg = sigletons.get(propertyDefiniton.getRef()); } else { arg = ConvertUtils.convert(propertyDefiniton.getValue(), propertyDescriptor.getPropertyType()); } setter.setAccessible(true); setter.invoke(bean, arg);//把引用对象注入到属性 } break; } } } } catch (Exception e) { e.printStackTrace(); } } } /*for (BeanDefinition beanDefinition : beanDefines) { try { //得到beanDefinition对应的类的所有属性 PropertyDescriptor[] propertyDescriptors = Introspector.getBeanInfo(Class.forName(beanDefinition.getClassName())).getPropertyDescriptors(); for ( PropertyDefiniton propertyDefiniton : beanDefinition.getProperties()) { //得到beans.xml中bean的所有property并循环遍历 for (PropertyDescriptor propertyDescriptor : propertyDescriptors) { Method method = propertyDescriptor.getWriteMethod(); if (method != null) { //比较beanDefinition中定义的属性与beans.xml中<bean/>节点下的property元素的name是否相同 if (propertyDescriptor.getName().equals(propertyDefiniton.getName())) { Object arg = null; if (propertyDefiniton.getRef() != null && !"".equals(propertyDefiniton.getRef())) { boolean flag = false; //将<bean/>节点下的<property/>元素与<beans/>下的所有<bean/>节点进行比较,确定<property/>所引用的<bean/>存在 for (BeanDefinition beanDefinition2 : beanDefines) { if (beanDefinition2.getId().equals(propertyDefiniton.getRef())) { flag = true; arg = Class.forName(beanDefinition2.getClassName()).newInstance(); break; } } if (flag == false) { throw new Exception("property元素所引用的bean不存在!"); } } else { //org.apache.commons.beanutils.ConvertUtils arg = ConvertUtils.convert(propertyDefiniton.getValue(), propertyDescriptor.getPropertyType()); } //防止setter方法是私有的,设置成可访问的 method.setAccessible(true); //这里不能重新实例化一个<bean/>对应的类,必须从用已经实例化并保存好的类, //否则在外部调用时属性还是没有被注入,如果用到属性将会是null Object object = sigletons.get(beanDefinition.getId()); method.invoke(object, arg); break; } } } } } catch (Exception e) { System.out.println(e.getMessage()); e.printStackTrace(); } }*/ } /** * 实例化bean对象 */ private void instanceBeans(){ for(BeanDefinition beanDefinition : beanDefines){ if (beanDefinition.getClassName()!= null && !"".equals(beanDefinition.getClassName().trim())) { try { sigletons.put(beanDefinition.getId(), Class.forName(beanDefinition.getClassName()).newInstance()); } catch (Exception e) { e.printStackTrace(); } } } } /** * 读取xml配置文件 * @param filename */ private void readXML(String filename) { SAXReader saxReader = new SAXReader(); Document document=null; try{ URL xmlpath = this.getClass().getClassLoader().getResource(filename); document = saxReader.read(xmlpath); Map<String,String> nsMap = new HashMap<String,String>(); nsMap.put("ns","http://www.springframework.org/schema/beans");//加入命名空间 XPath xsub = document.createXPath("//ns:beans/ns:bean");//创建beans/bean查询路径 xsub.setNamespaceURIs(nsMap);//设置命名空间 List<Element> beans = xsub.selectNodes(document);//获取文档下所有bean节点 for(Element element: beans){ String id = element.attributeValue("id");//获取id属性值 String clazz = element.attributeValue("class"); //获取class属性值 BeanDefinition beanDefine = new BeanDefinition(id, clazz); XPath propertysub = element.createXPath("ns:property"); propertysub.setNamespaceURIs(nsMap);//设置命名空间 List<Element> properties = propertysub.selectNodes(element);//获取文档下所有property节点 for(Element property : properties){ String name = property.attributeValue("name"); String ref = property.attributeValue("ref"); String value = property.attributeValue("value"); System.out.println("name = " + name + "\tref = " + ref + "\tvalue=" + value); PropertyDefiniton myProperty = new PropertyDefiniton(name, ref,value); beanDefine.getProperties().add(myProperty); } beanDefines.add(beanDefine); } }catch(Exception e){ e.printStackTrace(); } } /** * 获取bean实例 * @param beanName * @return */ public Object getBean(String beanName){ return sigletons.get(beanName); } }
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自己开发的注解:BlogResource.java
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package junit.test; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; @Retention(RetentionPolicy.RUNTIME) @Target({ElementType.FIELD,ElementType.METHOD}) public @interface BlogResource { public String name() default ""; }