spring ioc中实例化bean以及依赖注入bean和基本类型属性简单实现方案

Spring两个重要特性IOC和AOP，本文中简单实现bean的创建以及属性依赖注入。

实现步骤如下:

1、通过dom4j解析bean.xml文件,将bean对象以及依赖属性装入List。

2、遍历list，通过反射机制实例化对象。

3、遍历list，通过反射调用bean里的set方法注入依赖对象以及基本类型属性。

引入dom4j maven依赖

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"><modelVersion>4.0.0</modelVersion><groupId>myproject</groupId><artifactId>myproject</artifactId><packaging>war</packaging><version>0.0.1-SNAPSHOT</version><name>myproject Maven Webapp</name><url>http://maven.apache.org</url><dependencies><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>3.8.1</version><scope>test</scope></dependency><dependency><groupId>dom4j</groupId><artifactId>dom4j</artifactId><version>1.6.1</version></dependency><dependency><groupId>jaxen</groupId><artifactId>jaxen</artifactId><version>1.1.6</version></dependency><!-- https://mvnrepository.com/artifact/commons-beanutils/commons-beanutils --><dependency><groupId>commons-beanutils</groupId><artifactId>commons-beanutils</artifactId><version>1.8.3</version></dependency></dependencies><build><finalName>myproject</finalName></build></project>

spring bean配置文件

<beans xmlns="http://www.springframework.org/schema/beans"        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"        xmlns:context="http://www.springframework.org/schema/context"        xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"        xsi:schemaLocation="http://www.springframework.org/schema/beans             http://www.springframework.org/schema/beans/spring-beans-3.2.xsd             http://www.springframework.org/schema/mvc             http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd             http://www.springframework.org/schema/context             http://www.springframework.org/schema/context/spring-context-3.2.xsd             http://www.springframework.org/schema/aop             http://www.springframework.org/schema/aop/spring-aop-3.2.xsd             http://www.springframework.org/schema/tx             http://www.springframework.org/schema/tx/spring-tx-3.2.xsd ">              <bean id="orderDao" class="com.ocean.spring.bean.OrderDao">      </bean>            <bean id="orderService" class="com.ocean.spring.bean.OrderService">          <!-- 需要注入bean -->          <property name="orderDao" ref="orderDao"/>         <!-- 需要注入基本类型数据 -->          <property name="name" value="ocean"/>        <property name="id" value="56"/>    </bean>    </beans>

OrderService类

package com.ocean.spring.bean;public class OrderService {private OrderDao orderDao;private String name;private int id;public void updateOrder() {System.out.println(this.name+","+this.id);orderDao.updateOrder();}public void setName(String name) {this.name = name;}public void setId(int id) {this.id = id;}// set 方法提供依赖注入public void setOrderDao(OrderDao orderDao) {this.orderDao = orderDao;}}

OrderDao类

package com.ocean.spring.bean;    public class OrderDao {      public void updateOrder(){          System.out.println("更新订单信息");      }  } 

bean描述类

package com.ocean.spring.bean;    import java.util.ArrayList;  import java.util.List;  /**  * bean描述对象  * @author  *  */  public class BeanDefine {            private String id;      private String className;            private List<PropertiesDto> propertiesDtos = new ArrayList<PropertiesDto>();            public BeanDefine(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<PropertiesDto> getPropertiesDtos() {          return propertiesDtos;      }      public void setPropertiesDtos(List<PropertiesDto> propertiesDtos) {          this.propertiesDtos = propertiesDtos;      }        }  

bean属性描述类

package com.ocean.spring.bean;/** * 属性描述对象 *  * @author *  */public class PropertiesDto {private String name;private String ref;private String value;public PropertiesDto() {}public PropertiesDto(String name, String ref, String value) {this.name = name;this.ref = ref;this.value = value;}public String getValue() {return value;}public void setValue(String value) {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;}}

模拟实现bean的实例化以及依赖注入类

package com.ocean.spring.bean;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.DocumentException;import org.dom4j.Element;import org.dom4j.XPath;import org.dom4j.io.SAXReader;public class SpringIoc {private List<BeanDefine> beanDefines = new ArrayList<BeanDefine>();private Map<String, Object> beans = new HashMap<String, Object>();public static void main(String[] args) {SpringIoc SpringIoc = new SpringIoc();SpringIoc.myIoc();OrderService orderService = (OrderService) SpringIoc.getBeans().get("orderService");orderService.updateOrder();// 如果报空指针则注入失败，如果打印出信息表示注入成功}public void myIoc() {// dom4j解析xmlreadXML("config/spring/spring-bean.xml");// 利用反射实例化beaninstanceBean();// bean的属性注入inject();}/** * dom4j解析xml *  * @param fileName */private void readXML(String fileName) {SAXReader saxReader = new SAXReader();URL url = this.getClass().getClassLoader().getResource(fileName);try {Map<String, String> nsMap = new HashMap<String, String>();nsMap.put("ns", "http://www.springframework.org/schema/beans");Document document = saxReader.read(url);XPath xPath = document.createXPath("//ns:beans/ns:bean");// 创建查询路径xPath.setNamespaceURIs(nsMap);List<Element> beans = xPath.selectNodes(document);for (Element element : beans) {String id = element.attributeValue("id");String className = element.attributeValue("class");BeanDefine beanDefine = new BeanDefine(id, className);// bean描述对象XPath propertysub = element.createXPath("ns:property");propertysub.setNamespaceURIs(nsMap);List<Element> properties = propertysub.selectNodes(element);if (properties != null && properties.size() > 0) {for (Element property : properties) {String name = property.attributeValue("name");String ref = property.attributeValue("ref");String value = property.attributeValue("value");if (name != null) {PropertiesDto propertiesDto = new PropertiesDto();// 属性描述对象propertiesDto.setName(name);if (ref != null) {propertiesDto.setRef(ref);}if (value != null) {propertiesDto.setValue(value);}beanDefine.getPropertiesDtos().add(propertiesDto);}}}beanDefines.add(beanDefine);}} catch (DocumentException e) {}}/** * 实例化 */private void instanceBean() {if (beanDefines == null || beanDefines.size() == 0) {System.out.println("容器中没有需要实例化的bean");return;}try {for (BeanDefine beanDefine : beanDefines) {beans.put(beanDefine.getId(), Class.forName(beanDefine.getClassName()).newInstance());}} catch (Exception e) {e.printStackTrace();}}/** * 依赖注入 */private void inject() {try {for (BeanDefine beanDefine : beanDefines) {List<PropertiesDto> propertiesDtos = beanDefine.getPropertiesDtos();if (propertiesDtos != null && propertiesDtos.size() > 0) {Object bean = beans.get(beanDefine.getId());PropertyDescriptor[] propertyDescriptors = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();for (PropertiesDto propertiesDto : propertiesDtos) {for (PropertyDescriptor propertyDescriptor : propertyDescriptors) {if (propertyDescriptor.getName().equals(propertiesDto.getName())) {Method setter = propertyDescriptor.getWriteMethod();// 获取属性的set方法if (propertiesDto.getRef() != null && !"".equals(propertiesDto.getRef())) {setter.invoke(bean, beans.get(propertiesDto.getRef()));// 将依赖的bean注入进来}String value = propertiesDto.getValue();if (value != null && !"".equals(value)) {// 用apache的ConvertUtils将基本类型属性注入进来setter.invoke(bean,ConvertUtils.convert(value, propertyDescriptor.getPropertyType()));}break;}}}}}} catch (Exception e) {}}public Map<String, Object> getBeans() {return beans;}}

工程目录结构图