模拟spring，自定义容器二（注解实现属性注入）

超、凢脫俗 2024-02-18 15:41 67阅读 0赞

**1.创建自定义的容器类（增加自定义注解）**

package cn.hq.customspring;
    
    import java.beans.IntrospectionException;
    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;
    
    /**
     * 自定义的spring容器
     *
     */
    public class HqClasspathXmlApplicationContext {
    	private List<BeanDefinition> beanDefinitions = new ArrayList<BeanDefinition>();
    	private Map<String,Object> singletons = new HashMap<String,Object>();
    	
    	public HqClasspathXmlApplicationContext(String filename) {
    		this.readXML(filename);
    		this.instanceBeans();
    		this.annotationInject();
    		this.injectObject();
    	}
    
    	/**
    	 * 自定义注解注入
    	 */
    	private void annotationInject() {
    		for(String beanName : singletons.keySet()) {
    			Object bean = singletons.get(beanName);
    			if(bean!=null) {
    				try {
    					PropertyDescriptor[] ps = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();
    					
    					//setter方法上有注解
    					for(PropertyDescriptor propertyDescriptor : ps) {
    						Method setter = propertyDescriptor.getWriteMethod();
    						if(setter!=null && setter.isAnnotationPresent(HqResource.class)) { //setter上有HqResource注解
    							HqResource resource = setter.getAnnotation(HqResource.class);
    							Object value = null;
    							if(resource.name() !=null&& !"".equals(resource.name())) {
    								value = singletons.get(resource.name());
    							}else {
    								value = singletons.get(propertyDescriptor.getName());
    								if(value == null) {
    									for(String key : singletons.keySet()) {
    										//判断类型是否相同
    										if(propertyDescriptor.getPropertyType().isAssignableFrom(singletons.get(key).getClass())) {
    											value = singletons.get(key);
    											break;
    										}
    									}
    								}
    							}
    							setter.setAccessible(true);
    							setter.invoke(bean, value);							
    						}
    					}
    
    					//属性上有注解
    					Field[] fields = bean.getClass().getDeclaredFields();
    					for(Field field: fields) {
    						if(field.isAnnotationPresent(HqResource.class)) {
    							HqResource resource = field.getAnnotation(HqResource.class);
    							Object value = null;
    							if(resource.name() !=null&& !"".equals(resource.name())) {
    								value = singletons.get(resource.name());
    							}else {
    								value = singletons.get(resource.name());
    								if(value == null) {
    									for(String key : singletons.keySet()) {
    										//判断类型是否相同
    										if(field.getType().isAssignableFrom(singletons.get(key).getClass())) {
    											value = singletons.get(key);
    											break;
    										}
    									}
    								}
    							}
    							field.setAccessible(true);
    							field.set(bean, value);
    						}
    					}
    					
    					
    				} catch (Exception e) {
    					// TODO Auto-generated catch block
    					e.printStackTrace();
    				}
    			}
    		}
    	}
    
    	//为bean对象的属性注入值
    	private void injectObject() {
    		for(BeanDefinition beanDefinition : beanDefinitions) {
    			Object bean = singletons.get(beanDefinition.getId());
    			if(bean!=null) {
    				try {
    					PropertyDescriptor[] ps = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();
    					for(PropertyDefinition propertyDefinition : beanDefinition.getPropertys()) {
    						for(PropertyDescriptor propertyDescriptor : ps) {
    							if(propertyDefinition.getName().equals(propertyDescriptor.getName())) {
    								Method setter = propertyDescriptor.getWriteMethod(); //获取属性的set方法
    								if(setter != null) {
    									Object value = null;
    									if(propertyDefinition.getRef()!=null&&!"".equals(propertyDefinition.getRef().trim())) {
    										value = singletons.get(propertyDefinition.getRef());
    									}else {
    										value = ConvertUtils.convert(propertyDefinition.getValue(), propertyDescriptor.getPropertyType());
    									}
    									setter.setAccessible(true); // 设置为true 以防属性为private
    									setter.invoke(bean, value); //将引用对象注入到属性
    								}
    							}
    						}
    					}
    					
    				} catch (Exception e) {
    					e.printStackTrace();
    				}
    			}
    		}
    	}
    
    	//完成Bean实例化
    	private void instanceBeans() {
    		for(BeanDefinition beanDefinition : beanDefinitions) {
    				try {
    					if(beanDefinition.getClassName() != null && !"".equals(beanDefinition.getClassName().trim())) {
    						singletons.put(beanDefinition.getId(), Class.forName(beanDefinition.getClassName()).newInstance());
    					}
    				} catch (Exception e) {
    					e.printStackTrace();
    				} 
    		}
    	}
    
    	
    	//读取XML文件中的bean  
    	@SuppressWarnings("unchecked")
    	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 xPath = document.createXPath("//ns:beans/ns:bean"); //创建beans和bean查询路劲
    			xPath.setNamespaceURIs(nsMap); //设置命名空间
    			List<Element> beans = xPath.selectNodes(document); //获取文档下所有的bean节点
    			for(Element element:beans) {
    				String id = element.attributeValue("id");
    				String clazz = element.attributeValue("class");
    				BeanDefinition beanDefinition = new BeanDefinition(id,clazz);
    				
    				//读取bean的属性property节点
    				XPath xPathProperty = element.createXPath("ns:property"); //
    				xPathProperty.setNamespaceURIs(nsMap); //设置命名空间
    				
    				List<Element> propertys = xPathProperty.selectNodes(element);
    				for(Element property : propertys) {
    					String propertyName = property.attributeValue("name");
    					String propertyRef = property.attributeValue("ref");
    					String propertyValue = property.attributeValue("value");
    //					System.out.println("name=" + propertyName + "-----ref=" + propertyRef);
    					PropertyDefinition propertyDefinition = new PropertyDefinition(propertyName, propertyRef,propertyValue);
    					beanDefinition.getPropertys().add(propertyDefinition);
    				}
    				
    				
    				beanDefinitions.add(beanDefinition);
    			}
    			
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    	}
    	
    	/**
    	 * 获取bean实例
    	 * @param beanName
    	 * @return
    	 */
    	public Object getBean(String beanName) {
    		return singletons.get(beanName);
    	}
    	
    	
    }

**2.自定义注解类**

package cn.hq.customspring;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    /**
     * 自定义注解类
     */
    @Retention(RetentionPolicy.RUNTIME) //运行时期
    @Target({ElementType.FIELD,ElementType.METHOD}) //注解作用在字段上和方法上
    public @interface HqResource {
    	public String name() default "";
    }

**3.使用自定义注解**

package cn.hq.service.impl;
    
    import cn.hq.customspring.HqResource;
    import cn.hq.dao.StudentDao;
    import cn.hq.service.StudentService;
    
    public class StudentServiceImpl implements StudentService{
    
    
    	@HqResource
    	private StudentDao studentDao;
    	
    	public void setStudentDao(StudentDao studentDao) {
    		this.studentDao = studentDao;
    	}	
    	
    	public void save() throws Exception {
    		System.out.println("studentServiceImpl==>save()");
    		studentDao.add();
    	}
    
    	public void init() throws Exception {
    		System.out.println("studentServiceImpl==>init()");
    	}
    
    	public void destroy() throws Exception {
    		System.out.println("studentServiceImpl==>destroy()");
    		
    	}
    	
    }

**4.测试**

HqClasspathXmlApplicationContext hqApplicationContext = new HqClasspathXmlApplicationContext("beans.xml");
    		StudentService studentService = (StudentService)hqApplicationContext.getBean("studentService");
    		try {
    			studentService.save();
    		} catch (Exception e) {
    			e.printStackTrace();	
    		}