模拟spring，自定义容器一（属性注入、Bean的实例化）

傷城~ 2024-02-18 15:40 2阅读 0赞

**1.创建自定义的容器类**

package cn.hq.customspring;
    
    import java.beans.Introspector;
    import java.beans.PropertyDescriptor;
    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.injectObject();
    	}
    
    	//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.创建自定义的BeanDefinition类**

package cn.hq.customspring;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class BeanDefinition {
    	private String id;
    	private String className;
    	private List<PropertyDefinition> propertys = new ArrayList<PropertyDefinition>();
    	
    	public BeanDefinition(String id,String className) {
    		this.id = id;
    		this.className = className;
    	}
    	public String getId() {
    		return id;
    	}
    	public void setId(String id) {
    		this.id = id;
    	}
    	public String getClassName() {
    		return className;
    	}
    	public void setClassName(String className) {
    		this.className = className;
    	}
    	public List<PropertyDefinition> getPropertys() {
    		return propertys;
    	}
    	public void setPropertys(List<PropertyDefinition> propertys) {
    		this.propertys = propertys;
    	}
    	
    }

**3.创建自定义的PropertyDefinition类**

package cn.hq.customspring;
    
    public class PropertyDefinition {
    	private String name;
    	private String ref;
    	private String value;
    	
    	public PropertyDefinition(String name,String ref,String value) {
    		this.name = name;
    		this.ref = ref;
    		this.value = value;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public String getRef() {
    		return ref;
    	}
    	public void setRef(String ref) {
    		this.ref = ref;
    	}
    	public String getValue() {
    		return value;
    	}
    	public void setValue(String value) {
    		this.value = value;
    	}
    	
    	
    }

### 4. 创建spring的配置文件 ###

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="
            http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
            http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> 
    
    	
    	
    	
    	
    	
    	
    	
    
    	
    	
    	
    	
    	
    	
    	
    	 
    	<bean id="studentDao" class="cn.hq.dao.impl.StudentDaoImpl"></bean>
    	<bean id="studentService" class="cn.hq.service.impl.StudentServiceImpl">
    		<property name="studentDao" ref="studentDao"></property>
    		<property name="studentName" value="zzhua"></property>
    		<property name="studentAge" value="122"></property>
    		<property name="salary" value="122.98898"></property>
    	</bean>
    	
    	
    </beans>

**5.通过容器实例化对象**

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

**使用的jar包下载地址：**

http://download.csdn.net/download/u010879420/10012282