动手写简单实现注解SpringMVC框架

转自：http://blog.csdn.net/chaoyueygw/article/details/53393952 略作修改

 

1.第一步编写几个注解，名称作用与SpringMVC中相对应

 

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Controller {
	String value() default "";
}

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Service {
	String value() default "";
}


@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Quatifier {
	String value() default "";
}

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestMapping {
	String value() default "";
}

 

 

2.第二步 编写Servlet类，在init（）方法中 完成实例化和注入，以及建立映射关系。

①包扫描：将整个项目所有类扫描并保存起来，对应下面scanPackage（path）方法，包参数直接写死就行。

②过滤和实例化：将有Controller和Service注释的类过滤出来，实例化。并以注释value为key值，实例为value存储起来

③建立映射关系：将RequestMapping注释的value与注释的方法method对象存储起来

④注入：根据注解将Service实例注入到Controller中的属性

 

servlet代码如下：

 

@WebServlet("/")  
public class DispatcherServlet extends HttpServlet {  
    private static final long serialVersionUID = 1L;  
    List<String> packageNames = new ArrayList<String>();  
    // 所有类的实例，key是注解的value,value是所有类的实例  
    Map<String, Object> instanceMap = new HashMap<String, Object>();  
    Map<String, Object> handerMap = new HashMap<String, Object>();  
    public DispatcherServlet() {  
        super();  
    }  
    public void init() throws ServletException {  
        // 包扫描,获取包中的文件  
        scanPackage("com.chaoyue");  
        try {  
            filterAndInstance();  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
        // 建立映射关系  
        handerMap();  
        // 实现注入  
        ioc();  
    }  
  
    private void filterAndInstance() throws Exception {  
        if (packageNames.size() <= 0) {  
            return;  
        }  
        for (String className : packageNames) {  
            Class<?> cName = Class.forName(className.replace(".class", "").trim());  
            if (cName.isAnnotationPresent(Controller.class)) {  
                Object instance = cName.newInstance();  
                Controller controller = (Controller) cName.getAnnotation(Controller.class);  
                String key = controller.value();  
                instanceMap.put(key, instance);  
            } else if (cName.isAnnotationPresent(Service.class)) {  
                Object instance = cName.newInstance();  
                Service service = (Service) cName.getAnnotation(Service.class);  
                String key = service.value();  
                instanceMap.put(key, instance);  
            } else {  
                continue;  
            }  
        }  
    }  
  
    private void ioc() {  
        if (instanceMap.isEmpty())  
            return;  
        for (Map.Entry<String, Object> entry : instanceMap.entrySet()) {  
            // 拿到里面的所有属性  
            Field fields[] = entry.getValue().getClass().getDeclaredFields();  
            for (Field field : fields) {  
                field.setAccessible(true);// 可访问私有属性  
                if (field.isAnnotationPresent(Quatifier.class));  
                Quatifier quatifier = field.getAnnotation(Quatifier.class);  
                String value = quatifier.value();  
                field.setAccessible(true);  
                try {  
                    field.set(entry.getValue(), instanceMap.get(value));  
                } catch (IllegalArgumentException e) {  
                    e.printStackTrace();  
                } catch (IllegalAccessException e) {  
                    e.printStackTrace();  
                }  
            }  
        }  
    }  
  
    /** 
     * 扫描包下的所有文件 
     *  
     * @param Package 
     */  
    private void scanPackage(String Package) {  
        URL url = this.getClass().getClassLoader().getResource("/" + replaceTo(Package));// 将所有的.转义获取对应的路径  
        String pathFile = url.getFile();  
        File file = new File(pathFile);  
        String fileList[] = file.list();  
        for (String path : fileList) {  
            File eachFile = new File(pathFile + path);  
            if (eachFile.isDirectory()) {  
                scanPackage(Package + "." + eachFile.getName());  
            } else {  
                packageNames.add(Package + "." + eachFile.getName());  
            }  
        }  
    }  
  
    /** 
     * 建立映射关系 
     */  
    private void handerMap() {  
        if (instanceMap.size() <= 0)  
            return;  
        for (Map.Entry<String, Object> entry : instanceMap.entrySet()) {  
            if (entry.getValue().getClass().isAnnotationPresent(Controller.class)) {  
                Controller controller = (Controller) entry.getValue().getClass().getAnnotation(Controller.class);  
                String ctvalue = controller.value();  
                Method[] methods = entry.getValue().getClass().getMethods();  
                for (Method method : methods) {  
                    if (method.isAnnotationPresent(RequestMapping.class)) {  
                        RequestMapping rm = (RequestMapping) method.getAnnotation(RequestMapping.class);  
                        String rmvalue = rm.value();  
                        handerMap.put("/" + ctvalue + "/" + rmvalue, method);  
                    } else {  
                        continue;  
                    }  
                }  
            } else {  
                continue;  
            }  
  
        }  
    }  
  
    private String replaceTo(String path) {  
        return path.replaceAll("\\.", "/");  
    }  
  
    @Override  
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {  
        this.doPost(req, resp);  
    }  
  
    @Override  
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {  
        String url = req.getRequestURI();  
        String context = req.getContextPath();  
        String path = url.replace(context, "");  
        Method method = (Method) handerMap.get(path);  
        SpringmvcController controller = (SpringmvcController) instanceMap.get(path.split("/")[1]);  
        try {  
            method.invoke(controller, new Object[] { req, resp, null });  
        } catch (IllegalAccessException e) {  
            e.printStackTrace();  
        } catch (IllegalArgumentException e) {  
            e.printStackTrace();  
        } catch (InvocationTargetException e) {  
            e.printStackTrace();  
        }  
    }  
  
}  

 

 

Controller类代码如下：

 

@Controller("controller")  
public class SpringmvcController {  
    @Quatifier("MyServiceImpl")  
    MyService myService;  

    @RequestMapping("insert")  
    public String insert(HttpServletRequest request, HttpServletResponse response, String param) {  
        myService.insert(null);   
        return null;  
    }  
  
    @RequestMapping("delete")  
    public String delete(HttpServletRequest request, HttpServletResponse response, String param) {  
        myService.delete(null);  
        return null;  
    }  
  
    @RequestMapping("update")  
    public String update(HttpServletRequest request, HttpServletResponse response, String param) {  
        myService.update(null);  
        return null;  
    }  
  
    @RequestMapping("select")  
    public String select(HttpServletRequest request, HttpServletResponse response, String param) {  
        myService.select(null);   
        return null;  
    }  
}  

 

 

Service接口及实现类如下：

public interface MyService {  
    int insert(Map map);  
  
    int delete(Map map);  
  
    int update(Map map);  
  
    int select(Map map);  
}  

@Service("MyServiceImpl")  
public class MyServiceImpl implements MyService {  
    @Override  
    public int insert(Map map) {  
        System.out.println("MyServiceImpl:" + "insert");  
        return 0;  
    }  
  
    @Override  
    public int delete(Map map) {  
        System.out.println("MyServiceImpl:" + "delete");  
        return 0;  
    }  
  
    @Override  
    public int update(Map map) {  
        System.out.println("MyServiceImpl:" + "update");  
        return 0;  
    }  
  
    @Override  
    public int select(Map map) {  
        System.out.println("MyServiceImpl:" + "select");  
        return 0;  
    }  
}  

 

这样运行项目，输入地址：localhost:8080/项目名/controller/insert

控制台打印 MyServiceImplinsert