开发笔记:模仿Spring实现注解注入

package com.yck.yebatis;
import java.io.File;
import java.io.FileFilter;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import com.yck.bean.Function;
import com.yck.bean.MapperBean;
import com.yck.exception.NoConfigFileException;
import com.yck.util.DataUtil;
public class DaoFactory implements BeanFactory
{

private static Map beans;

static
{
configDao();
}


@Override
public Object getBean(String beanName) //暴露获取Bean的方法
{
return beans.get(beanName);
}




private static void configDao() //初始化
{
Map map = new HashMap();
try
{
File[] files = getAllFiles();
for(File f:files)
{
MapperBean mapper = readMapper(f.getPath());
Object obj = implDao(mapper);
map.put(mapper.getProxyName(), obj);
}
} catch (NoConfigFileException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}

beans = map;
}



/**
* 得到所有的mapper.xml文件
* @return
* @throws NoConfigFileException
*/
private static File[] getAllFiles() throws NoConfigFileException
{
File configPath = new File("src/mapper"); //为了简单起见，规定写在该目录下
FileFilter fileFilter = new FileFilter() //写过滤器，筛选后缀为.xml的文件
{

@Override
public boolean accept(File pathname)
{
String str = pathname.getName().toLowerCase();
if(str.endsWith(".xml"))
return true;
return false;
}
};

File[] files = configPath.listFiles(fileFilter);
if(files == null || files.length == 0) //如果没有这样的文件，抛出异常
{
files = null;
throw new NoConfigFileException();
}
return files;
}


/**
* 通过读取配置文件实现dao接口
* @param path
* @return
*/
private static Object implDao(MapperBean mapper)
{
ClassLoader classLoader = DaoFactory.class.getClassLoader();
Class interfaze = null;
try
{
interfaze = classLoader.loadClass(mapper.getInterfaceName()); //加载一个接口类
} catch (ClassNotFoundException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}

/**
* 下面这几句相当重要了，是用xml文件实现dao接口的核心代码，因为数据库相关的大量工作我之前都写过了，所以这个看起来代码量很少
* 我也不太懂下面这个东西，我查API查了相当久，一开始写总是错，因为我理解错了InvocationHandler接口下那个方法的Object数组参数
* 它应该理解为一个可变长数组，而不是必须为数组
*/
Object instanze = Proxy.newProxyInstance(classLoader, new Class[]{interfaze}, new InvocationHandler(){
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
{
List list = mapper.getList();
Object obj = null;
for(Function f:list)
{
if(f.getFuncName().equals(method.getName()))
{
/**
* 判断是不是select语句，是则调用DateUtil的select方法
* 否则调用update的方法
*/
if(f.getSqltype().equals("select"))
{
if("java.util.ArrayList".equals(f.getResultType()))
{
if(f.isParameter())
obj = DataUtil.selectForBeanList(Class.forName(f.getResultOf()), f.getSql(), args);
else obj = DataUtil.selectForBeanList(Class.forName(f.getResultOf()), f.getSql());
}
else
{
if(f.isParameter())
obj = DataUtil.selectForBean(Class.forName(f.getResultType()), f.getSql(), args);
else obj = DataUtil.selectForBean(Class.forName(f.getResultType()), f.getSql());
}
}

else
{
if(f.isParameter())
obj = DataUtil.updata(f.getSql(), args);
else obj = DataUtil.updata(f.getSql());
}
}
}
return obj;
}
});
return instanze;
//返回这个接口，即mapper.getInterfaceName()这个接口

}

/**
* 读取xml文件的信息
* @param path
* @return
*/
private static MapperBean readMapper(String path)
{
File file = new File(path);
SAXReader reader = new SAXReader();
MapperBean mapper = new MapperBean();
try
{
Document doc = reader.read(file);
Element root = doc.getRootElement(); //读取根节点 即dao节点
mapper.setInterfaceName(root.attributeValue("class").trim()); //把dao节点的class值存为接口名
mapper.setProxyName(root.attributeValue("id").trim()); //把id值设为代理名
List list = new ArrayList(); //用来存储方法的List
for(Iterator rootIter = root.elementIterator();rootIter.hasNext();) //遍历根节点下所有子节点
{
Function fun = new Function(); //用来存储一条方法的信息
Element e = (Element) rootIter.next();
String sqltype = e.getName().trim();
String funcName = e.attributeValue("id").trim();
String sql = e.getText().trim();
String resultType = e.attributeValue("resultType").trim();
String resultOf = "";
if("java.util.ArrayList".equals(resultType))
resultOf = e.attributeValue("resultOf").trim();
String parameter = e.attributeValue("parameter");
fun.setSqltype(sqltype);
fun.setFuncName(funcName);
fun.setResultType(resultType);
fun.setSql(sql);
fun.setResultOf(resultOf);
fun.setParameter("true".equals(parameter));
list.add(fun);
}
mapper.setList(list);

} catch (DocumentException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
return mapper;
}

package com.yck.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface SelfInject
{
String value();
}

package com.yck.service;
import com.yck.annotation.SelfInject;
import com.yck.bean.User;
import com.yck.dao.IUserDao;
public class UserService
{
@SelfInject(value="userdao")
private IUserDao userdao;

public User find(Integer id)
{
return userdao.selectById(id);
}
}

xml version="1.0" encoding="UTF-8"?>
<services>
<service id="userService" class="com.yck.service.UserService"/>
services>

package com.yck.yebatis;
import java.io.File;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import com.yck.annotation.SelfInject;
import com.yck.bean.ServiceBean;
public class ServiceFactory implements BeanFactory
{
private static DaoFactory daoFactory = new DaoFactory();
private static Map beans;

static
{
configService();
}

/**
* 暴露获取方法
*/
@Override
public Object getBean(String beanName)
{
return beans.get(beanName);
}
/**
* 静态初始化方法
*/
private static void configService()
{
Map map = new HashMap();
List list= getServiceBeans();
for(ServiceBean service:list)
{
map.put(service.getProxyName(), implService(service));
}
beans = map;
}

/**
* 读取所有的Service配置
* @return
*/
private static List getServiceBeans()
{
SAXReader reader = new SAXReader();
List list = new ArrayList();
try
{
Document doc = reader.read(new File("src/service/service.xml"));
Element root = doc.getRootElement();
for(Iterator iter = root.elementIterator("service");iter.hasNext();)
{
Element e = (Element) iter.next();
String proxyName = e.attributeValue("id");
String className = e.attributeValue("class");
ServiceBean bean = new ServiceBean(proxyName, className);
list.add(bean);

}
} catch (DocumentException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
return list;

}


/**
* 实例化Service并注入所需依赖
* @param service
* @return
*/
public static Object implService(ServiceBean service)
{
Object obj = null;
try
{
obj = Class.forName(service.getClassName()).newInstance();
Class c = obj.getClass();
Field[] fields = c.getDeclaredFields();
for(Field f:fields)
{
Annotation[] annotations = f.getAnnotations();
for(Annotation a:annotations)
{
if(a instanceof SelfInject)
{
Object o = daoFactory.getBean(((SelfInject) a).value());
try
{
f.setAccessible(true);
f.set(obj,o);
f.setAccessible(false);
} catch (IllegalArgumentException | IllegalAccessException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}

} catch (ClassNotFoundException | InstantiationException | IllegalAccessException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
return obj;
}
}

package com.yck.test;
import com.yck.bean.User;
import com.yck.dao.IUserDao;
import com.yck.service.UserService;
import com.yck.yebatis.DaoFactory;
import com.yck.yebatis.ServiceFactory;
public class Test2
{

public static void main(String[] args)
{
DaoFactory bf = new DaoFactory();
IUserDao userdao = (IUserDao) bf.getBean("userdao");
User u = userdao.selectById(2);
System.out.println(u);

ServiceFactory sf = new ServiceFactory();
UserService userService = (UserService) sf.getBean("userService");
User us = userService.find(2);

System.out.println(us);


}
}