通过注解实现一个简易的Spring mvc框架

 

   1.首先我们来搭建架构,就建一个普通的javaweb项目就OK了,具体目录如下:

 

  

  对于小白来说可以细看后面web.xml的配置,对javaweb有点研究可以忽略而过后面的web.xml配置。

      2.先上代码,运行起整个项目。再来聊聊思路。

    

          (1).Controller注解
     
复制代码
package com.wuqi.annotation;
import java.lang.annotation.*;
/**
 * Created by wuqi on 2017/3/22.
 */
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Controller {
    String value() default "";
}
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     (2).Quatifier注解
      
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package com.wuqi.annotation;

import java.lang.annotation.*;

/**
 * Created by wuqi on 2017/3/25.
 */
@Target({ ElementType.FIELD }) // 代表注解的注解
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Quatifier {
    String value() default "";
}
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      (3).RequestMapping注解
     
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package com.wuqi.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
 * Created by Shock on 2017/3/22.
 */
@Target({ ElementType.METHOD }) // 在方法上的注解
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestMapping {
    String value() default "";
}
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          (4).Service注解
     
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package com.wuqi.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
 * Created by Shock on 2017/3/22.
 */
@Target({ ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Service {
    String value() default "";
}
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 --------------------------------------------------------------------------------------------------------------------------

   

     (1).MyService接口
    
复制代码
package com.wuqi.service.impl;

import java.util.Map;

/**
 * Created by wuqi on 2017/3/23.
 */
public interface MyService {

    int insert(Map map);

    int delete(Map map);

    int update(Map map);

    int select(Map map);

}
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     (2).MyServiceImpl类
    
复制代码
package com.wuqi.service.impl;
import com.wuqi.annotation.Service;

import java.util.Map;
/**
 * Created by wuqi on 2017/3/23.
 */
@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;
    }
}
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      (3).SpringmvcService接口
    
复制代码
package com.wuqi.service.impl;

import java.util.Map;

/**
 * Created by wuqi on 2017/3/23.
 */
public interface SpringmvcService {
    int insert(Map map);

    int delete(Map map);

    int update(Map map);

    int select(Map map);
}
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   (4).MyServiceImpl类
    
复制代码
package com.wuqi.service.impl;
import com.wuqi.annotation.Service;

import java.util.Map;
/**
 * Created by wuqi on 2017/3/23.
 */
@Service("SpringmvcServiceImpl")
public class SpringmvcServiceImpl implements SpringmvcService{
    @Override
    public int insert(Map map) {
        System.out.println("SpringmvcServiceImpl:" + "insert");
        return 0;
    }
    @Override
    public int delete(Map map) {
        System.out.println("SpringmvcServiceImpl:" + "delete");
        return 0;
    }
    @Override
    public int update(Map map) {
        System.out.println("SpringmvcServiceImpl:" + "update");
        return 0;
    }
    @Override
    public int select(Map map) {
        System.out.println("SpringmvcServiceImpl:" + "select");
        return 0;
    }

}
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 --------------------------------------------------------------------------------------------------------------------------

   

  (1).SpringmvcController类
  
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package com.wuqi.controller;
import com.wuqi.annotation.*;
import com.wuqi.service.impl.MyService;
import com.wuqi.service.impl.SpringmvcService;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * Created by wuqi on 2017/3/23.
 */
@Controller("wuqi")
public class SpringmvcController {
    @Quatifier("MyServiceImpl")
    MyService myService;
    @Quatifier("SpringmvcServiceImpl")
    SpringmvcService smService;

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

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

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

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

  

      (1).DispatcherServlet类继承 javax.servlet.http.HttpServlet类
  
复制代码
package com.wuqi.servlet;

import com.wuqi.annotation.*;
import com.wuqi.controller.SpringmvcController;
import java.io.File;
import java.io.IOException;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
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 javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Created by Shock on 2017/3/23.
 */
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(ServletConfig config) throws ServletException {
        // 包扫描,获取包中的文档
        scanPackage("com.wuqi");
        try {
            filterAndInstance();
        } catch (Exception e) {
            e.printStackTrace();
        }
        // 创建映射关系
        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();
                }
            }
        }
        SpringmvcController wuqi = (SpringmvcController) instanceMap.get("wuqi");
        System.out.print(wuqi);
    }

    /**
     * 扫描包下的所有文档
     *
     * @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());
            }
        }
    }

    /**
     * 创建映射关系
     */
    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();
        }
    }
}
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所有的代码已经贴上,还有个web.xml

  
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<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
          http://java.sun.com/xml/ns/javaee/web-app_3_1.xsd"
           version="3.1">
    <servlet>
        <servlet-name>testServlet</servlet-name>
        <servlet-class>com.wuqi.servlet.DispatcherServlet</servlet-class>
    </servlet>
    <!-- ... -->
    <servlet-mapping>
        <servlet-name>testServlet</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
</web-app>
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  3.好了代码已经贴上了,现在需要来说说思路,因为有代码了,所以用代码来将思路,这样更容易理解代码的含义。之后可以根据自己的程度去试着写。

  •     首先我们需要扫描包中的所有文档(DispatcherServlet -> init(ServletConfig config) -> scanPackage("com.wuqi")),也就是含有注解的文档。然后将该包下的所有文档都存入packageNames集合中。
  •        这时我们拿到了包下所有的文档,但我们只需要含有我们指定注解的那部分文档,因此需要过滤出我们想要的文档即可,并且在过滤的过程中,我们可以将过滤出来的类通过Class.forName来直接实例化并储存起来。存放到instanceMap集合中,并为其设置对应的key值,该key值就是类注解的value。
  •           然后遍历instanceMap集合中的所有对象,获取指定注解的对象,并通过反射获取该对象的所有的方法,遍历所有的方法,将指定注解的方法存入handerMap,key为拼接字符串("/" + 对象变量名 + "/" + 方法名),value为方法(Method)。
  •           然后我们可以遍历instanceMap集合中的所有对象,通过反射获取对象的所有属性值(字段)集合,然后遍历属性值集合,将属性值含有指定注解的,通过Field的set方法为该属性值赋值,这时就将对象注入了。(也就是往Controller中注入Service对象)
  •          最后就可以通过反射的invoke方法调用某个对象的某个方法。(此时对象存于instanceMap,而方法都存于handerMap)

 

参考链接:

关键词:map import string wuqi java public com servlet controller class

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