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 "";
}