编码实现Spring 利用@Resource注解实现bean的注入，xml实现基本数据类型的注入

首先分析。

1： 肯定要利用dom4j读取xml配置文件，将所有的bean的配置信息读取出来

2： 利用反射技术，实例化所有的bean

3： 写注解处理器， 利用注解和内省实现依赖对象的注入。

4： 利用XML中<property>信息，通过内省beanUtils实现基本数据类型的注入

实现：

package cn.gbx.example;

import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.io.File;
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 MyClassPathXmlApplicationContext {
	private List<DefBean> defBeans = new ArrayList<DefBean>();
	private Map<String, Object> singletons = new HashMap<String, Object>();

	public MyClassPathXmlApplicationContext(String filename) {
		this.readXML(filename);
		this.instanceBean();
		this.injectAnotation();
		this.injectXML();

	}

	//注入基本类型的属性
	private void injectXML() {
		//枚举bean
		for (DefBean defBean : defBeans) {
			Object bean = singletons.get(defBean.getId());
			if (bean != null) {
				//枚举该bean的Property看有没有基本数据类型的注入
				for (DefProperty defProperty : defBean.getDefPropertys()) {
					if (defProperty.getValue() != null){
						try {
							PropertyDescriptor[] ps = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();
							for (PropertyDescriptor p : ps) {
								if (p.getName().equals(defProperty.getName())) {
									Method setter = p.getWriteMethod();
									//保证有set方法
									if (setter != null) {
										Object value = ConvertUtils.convert(defProperty.getValue(), p.getPropertyType());
										setter.setAccessible(true);
										setter.invoke(bean, value);
									}
									break;
								}
							}
						} catch (Exception e) {
							// TODO Auto-generated catch block
							e.printStackTrace();
						}
					}
				}
			}
		}
	}

	//注解处理器
	private void injectAnotation() {
		//枚举实例化的bean
		for (String key : singletons.keySet()) {
			Object bean = singletons.get(key);
			if (bean != null) {

				/*
				 * 检查setter方法
				 */
				try {
					PropertyDescriptor[] ps = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();
					//枚举每个bean的属性
					for (PropertyDescriptor p : ps) {
						Method setter = p.getWriteMethod();
						Object value = null;
						//存在set方法， 并且有setter上边有Resource注解
						if (setter != null && setter.isAnnotationPresent(GbxResource.class)){
							GbxResource gbxResource = setter.getAnnotation(GbxResource.class);
							//若有name 则按name查找
							if (gbxResource.name() != null && !"".equals(gbxResource.name())) {
								value = singletons.get(gbxResource.name());
							} else { //若没有，先安名字查找， 再按数据类型查找
								value = singletons.get(p.getName());
								if (value == null) {
									for (String key2 : this.singletons.keySet()) {
										if (p.getPropertyType().isAssignableFrom(this.singletons.get(key2).getClass())) {
											value = this.singletons.get(key2);
											break;
										}
									}
								}
							}
							setter.setAccessible(true);
							setter.invoke(bean, value);
						}
					}
				} catch (Exception e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}

				/*
				 * 检查字段
				 */
				 Field[] fileds = bean.getClass().getDeclaredFields();
				 for (Field field : fileds) {
					 if (field.isAnnotationPresent(GbxResource.class)) {
						 GbxResource gbxResource = field.getAnnotation(GbxResource.class);
						 Object value = null;
						 if (gbxResource.name() != null && !"".equals(gbxResource.name())) {
							 value = this.singletons.get(gbxResource.name());
						 } else {
							 value = this.singletons.get(field.getName());
							 if (value == null) {
								for (String key2 : this.singletons.keySet()) {
									if (field.getType().isAssignableFrom(this.singletons.get(key2).getClass())) {
										value = this.singletons.get(key2);
										break;
									}
								}
							 }
						 }
						 field.setAccessible(true);
						 try {
							field.set(bean, value);
						} catch (IllegalAccessException e) {
							e.printStackTrace();
						}
					 }
				 }
			}
		}

	}

	//实例化bean对象
	private void instanceBean() {
		for (DefBean bean : defBeans) {
			System.out.println(bean.getId() + " :　" + bean.getClassName());
			if (bean.getClassName() != null && !"".equals(bean.getClassName())) {
				try {
					singletons.put(bean.getId(), Class.forName(bean.getClassName()).newInstance());
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}
	}
	//读取xml文件
	private void readXML(String filename) {
		SAXReader reader = new SAXReader();
		Document document = null;
		URL xmlPath = this.getClass().getClassLoader().getResource(filename);

		try {
			//的到document
			document = reader.read(xmlPath);
			//设置命名空间
			Map<String, String> nsMap = new HashMap<String, String>();
			nsMap.put("ns", "http://www.springframework.org/schema/beans");
			//创建查询路径
			XPath xPath = document.createXPath("//ns:beans/ns:bean");
			xPath.setNamespaceURIs(nsMap);

			List<Element> beans = xPath.selectNodes(document);
			DefBean defBean = null;
			for (Element e : beans) {
				String id = e.attributeValue("id");
				String className = e.attributeValue("class");
				defBean = new DefBean(id, className);

				XPath xPath2 = e.createXPath("ns:property");
				xPath2.setNamespaceURIs(nsMap);
				List<Element> propertys = xPath2.selectNodes(e);

				DefProperty defProperty = null;
				for (Element e2 : propertys) {
					String name = e2.attributeValue("name");
					String ref = e2.attributeValue("ref");
					String value = e2.attributeValue("value");

					defProperty = new DefProperty(name, ref, value);
					defBean.getDefPropertys().add(defProperty);
				}
				defBeans.add(defBean);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public Object getBean(String key) {
		return singletons.get(key);
	}
}

　　

package cn.gbx.serviceimpl;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

import javax.annotation.Resource;

import org.springframework.beans.factory.annotation.Autowired;

import cn.gbx.daoimpl.PersonDao;
import cn.gbx.example.GbxResource;
import cn.gbx.service.PersonService;

public class PersonServiceImpl implements PersonService {
	@GbxResource
	private PersonDao personDao;
	private String name;

	public void save() {
		personDao.save();
		System.out.println("Name = " + name);
		System.out.println("service层的 save方法");
	}

	public void setPersonDao(PersonDao personDao) {
		this.personDao = personDao;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public PersonDao getPersonDao() {
		return personDao;
	}

}

　　

注解：

package cn.gbx.example;

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.METHOD, ElementType.FIELD})
public @interface GbxResource {
	public String name() default "";
}