自己实现一个简易的SpringMVC

上回实现了一个简易的Spring，那就顺便实现一些SpringMVC吧。由于有了上回的基础，这回实现比较快，晚饭前架构了一下，一晚上就写得差不多了。自己实现的架构比较简单，下面简单介绍一下。

源码下载：http://download.csdn.net/detail/jobsandczj/9844308

实现思路及工作流程：

定义一个DispatcherServlet，用来做请求入口。初始化时，去读取配置文件，获得Controller的包，然后“注入”Controller。SpringMVC它本身是有自己的IoC容器的，用来注入Controller以及它的组件，但IoC我在Spring里玩过了，这回就没有写依赖注入。但完事后发现其实也没省多少功夫，终归还是要扫包，解析的。

得到Controller后就构建Handler。让每个Handler与一个请求路径对应，我只定义了两种类型的Handler，一个是处理页面转发的，一个是返回Json数据的。每种Handler都有它的适配器，这就让Controller的方法设置参数少了很多约束，只要是request，response，session这仨家伙就行。

最后初始化适配器列表，以便在接收到请求后适配。

下面是Handler抽象类：

package MySpringMVC.springmvc;

import java.lang.reflect.Method;

/**
 * Created by 10033 on 2017/5/16.
 */
public abstract class Handler {
    protected Method method;
    protected Object controller;
    protected Class[] params;
    protected RequestMethod requestMethod;

    public Handler(Method method, Object controller, Class[] params, RequestMethod requestMethod) {
        this.method = method;
        this.controller = controller;
        this.params = params;
        this.requestMethod = requestMethod;
    }

    public Method getMethod() {
        return method;
    }

    public void setMethod(Method method) {
        this.method = method;
    }

    public Object getController() {
        return controller;
    }

    public void setController(Object controller) {
        this.controller = controller;
    }

    public Class[] getParams() {
        return params;
    }

    public void setParams(Class[] params) {
        this.params = params;
    }

    public RequestMethod getRequestMethod() {
        return requestMethod;
    }

    public void setRequestMethod(RequestMethod requestMethod) {
        this.requestMethod = requestMethod;
    }
}

下面这个是操作工具类，进行方法参数适配和适配器列表初始化

package MySpringMVC.utils;

import MySpringMVC.springmvc.ClasspathPackageScanner;
import MySpringMVC.springmvc.HandlerAdapter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.util.List;

/**
 * Created by 10033 on 2017/5/16.
 */
public class OperationUtil {
    private static final Logger logger = LoggerFactory.getLogger(OperationUtil.class);
    private static final String ADAPTER_PACKAGE="MySpringMVC.springmvc";
    public static int makeObjectsByClasses
            (Class[] classes, Object[] objects, HttpServletRequest request, HttpServletResponse response) throws Exception {
        int cou=0;
        for(Class cla:classes) {
            if(cla==HttpServletRequest.class) {
                objects[cou++]=request;
            } else if(cla==HttpServletResponse.class) {
                objects[cou++]=response;
            } else if(cla==HttpSession.class) {
                objects[cou++]=request.getSession();
            } else {
                throw new Exception("控制器参数错误");
            }
        }
        return cou;
    }

    public static void initHandlerAdapterList(List<HandlerAdapter> list) {
        try {
            List<String> classStringList=new ClasspathPackageScanner(ADAPTER_PACKAGE).getFullyQualifiedClassNameList();
            for(String s:classStringList) {
                Class cla=Class.forName(s);

                //实现了HandlerAdapter接口
                if (HandlerAdapter.class.isAssignableFrom(cla)) {
                    Object obj=cla.newInstance();
                    list.add((HandlerAdapter) obj);
                }

            }
        } catch (IOException e) {
            logger.error(e.getMessage());
        } catch (ClassNotFoundException e) {
            logger.error(e.getMessage());
        } catch (IllegalAccessException e) {
            logger.error(e.getMessage());
        } catch (InstantiationException e) {
            logger.error(e.getMessage());
        }
    }

}

这是DispatcherServlet类，进行初始化和控制器调度，为了管理静态资源要进行servlet注册。

package MySpringMVC.springmvc;

import MySpringMVC.utils.OperationUtil;
import MySpringMVC.utils.PropertiesReaderUtil;
import MySpringMVC.utils.StringUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRegistration;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * Created by 10033 on 2017/5/16.
 */
public class DispatcherServlet extends HttpServlet {

    private static final Logger logger = LoggerFactory.getLogger(DispatcherServlet.class);
    private String configName;
    private Map<String, String> configMap;
    private static final String SCAN_PACK="scan.package";
    private static final String VIEWPATH_STATIC="viewpath.static";
    private HandlerMap handleMap;
    private List<HandlerAdapter> handlerAdapters = new ArrayList<HandlerAdapter>();

    //初始化
    public void init(String configName) throws ServletException {
        super.init();
//        configName=getInitParameter("contextConfigLocationName");
        configMap= PropertiesReaderUtil.getProperties(configName);

        String packages=configMap.get(SCAN_PACK);//获得扫描包
        DispatchHelper.setMap(configMap);

        try {
            List<String> list=new ClasspathPackageScanner(packages).getFullyQualifiedClassNameList();
            handleMap=new HandlerMap(list);
        } catch (IOException e) {
            logger.error(e.getMessage());
        }

        OperationUtil.initHandlerAdapterList(handlerAdapters);

    }

    @Override
    public void init(ServletConfig config) throws ServletException {
        init(config.getInitParameter("contextConfigLocationName"));
        ServletContext servletContext=config.getServletContext();
        /*ServletRegistration servletRegistration = servletContext.getServletRegistration("jsp");
        servletRegistration.addMapping("/WEB-INF/jsps*//*");*/

        ServletRegistration servletRegistration2 = servletContext.getServletRegistration("default");
        String[] staticString=configMap.get(VIEWPATH_STATIC).split(";");

        for(int i=0;i<staticString.length;i++) {
            servletRegistration2.addMapping(staticString[i].toLowerCase()+"/*");
        }

    }

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //获取请求路径
        String requestUrl=StringUtil.getRequestURL(req);

        Handler handler=handleMap.getHandler(requestUrl,req.getMethod());
        if(null!=handler) {
            for(HandlerAdapter handlerAdapter:handlerAdapters) {
                if(handlerAdapter.support(handler)) {
                    handlerAdapter.setHandler(handler);
                    handlerAdapter.execute(req,resp);
                    break;
                }
            }
        }else {
            resp.sendError(HttpServletResponse.SC_NOT_FOUND);
        }

    }
}

这回还是有一些不足的，一是没实现IoC，当然这是自己偷懒。但还有一个不足就是，由于前端只支持JSP，所以View，Model这些也都没管。