探讨Non-Struts的Java Web开发

      开发Java Web项目时，如果不采用Struts、WebWork、SpringMVC等MVC框架，而使用原始的Servlet API时，该怎么开发呢？

      Struts 1.x采用了一个有“总控制器”作用的Servlet处理所有的请求，而Struts 2.x则采用了Filter。两者各有优缺点。我个人比较喜欢Struts2的一种URI约定形式，类似于“.../member!add.action ”、“.../abc/articles!list.action”的形式。在这里，我们本例也采取了Struts2的这种URI约定形式。即：

目录/目录/.../类名!方法名.后缀

      我们也采用Struts2的Filter主控方式，开发一个javax.servlet.Filter的子类，用来处理所有请求，再在这个Filter里获取访问的URI，从URI字符串中提取业务实体类和访问方法，然后根据Java的反射API，动态地创建类对象，动态地执行相应的业务方法。这个Filter我命名为"org.mvcgo.filter.ControllerFilter"。

在web.xml文件中，配置这个Filter，代码如下：

<filter>
	<filter-name>ControllerFilter</filter-name>
	<filter-class>org.mvcgo.filter.ControllerFilter</filter-class>
	<init-param>
		<param-name>suffix</param-name>
		<param-value>go</param-value>
	</init-param>
	<init-param>
		<param-name>encoding</param-name>
		<param-value>utf-8</param-value>
	</init-param>
	<init-param>
		<param-name>package</param-name>
		<param-value>org.mvcgo.action</param-value>
	</init-param>
</filter>
<filter-mapping>
	<filter-name>ControllerFilter</filter-name>
	<url-pattern>/*</url-pattern>
</filter-mapping>

 

      上面的代码中，ControllerFilter内置参数suffix、encoding分别表示URI的后缀和编码，package表示“根包”，所谓“根包”，这是学习了Struts2的URI命名规则，如上面配置的"org.mvcgo.action"，若有个Action类名为"org.mvcgo.action.infos.MemberGo.java"，则相应的访问路径为.../PROJECT_NAME/infos/member.go。这个参数都会在我写的"org.mvcgo.filter.ControllerFilter"类中用到。

      下面，我们来分析一下“org.mvcgo.filter.ControllerFilter”类，类的头部代码如下：

package org.mvcgo.filter;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.mvcgo.action.BaseGo;
import org.mvcgo.utils.StringUtil;

public class ControllerFilter implements Filter{...}

       在ControllerFilter里定义的成员属性如下：

	private FilterConfig filterConfig;
	
	//配置ControllerFilter时,对应于init-param中的param-name
	private static final String SUFFIX_NAME = "suffix";			//前缀的"param-name"
	private static final String ENCODING_NAME = "encoding";		//编码的"param-name"
	private static final String PACKAGE_NAME = "package";		//Go的基包的"param-name"
	
	//init-param的默认初始化值
	private String SUFFIX_VALUE_DEFAULT = "go";			//默认前缀
	private String ENCODING_VALUE_DEFAULT = "UTF-8";		//默认编码
	private String PACKAGE_VALUE_DEFAULT;

 

 重写Filter的init方法，执行初始化：

    /**
     * 重写Filter的init方法,执行初始化操作
     */
	public void init(FilterConfig filterConfig) throws ServletException {
		this.filterConfig = filterConfig;
		
		//初始化Go访问的后缀
		String suffix = filterConfig.getInitParameter(SUFFIX_NAME);
		if(null != suffix && !"".equals(suffix)) {
			this.SUFFIX_VALUE_DEFAULT = suffix;
		}
		
		//初始化编码
		String encoding = filterConfig.getInitParameter(ENCODING_NAME);
		if(null != encoding && !"".equals(encoding)){
			this.ENCODING_VALUE_DEFAULT = encoding;
		}
		
		//初始化Go类的基包
		String basePackage = filterConfig.getInitParameter(PACKAGE_NAME);
		if(null != basePackage && !"".equals(basePackage)) {
			this.PACKAGE_VALUE_DEFAULT = basePackage;
		} else {
			throw new ControllerDeployException("读取web.xml中ControllerFilter的初始化参数失败，请检查" + PACKAGE_NAME + "是否配置正确...");
		}
	}

 

初始化完后，会自动执行doFilter方法，代码如下：

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
	
	//强制转换request和response
	HttpServletRequest httpRequest = (HttpServletRequest) request;
	HttpServletResponse httpResponse = (HttpServletResponse) response;
	
	//设置HttpServletRequest的编码格式
	httpRequest.setCharacterEncoding(ENCODING_VALUE_DEFAULT);
	
	//获取请求的URI,如请求http://127.0.0.1:8080/mvcgo/info/user!save.go?id=7,会得到"/mvcgo/info/user!save.go"
	String requestURI = httpRequest.getRequestURI();
	System.out.println("url = " + requestURI);
	
	if(requestURI.endsWith("." + SUFFIX_VALUE_DEFAULT)) {
		String packageClassName = PACKAGE_VALUE_DEFAULT;		//包类名,即类的全名
		String[] segs = requestURI.split("/");
		for(int i = 2 ; i < segs.length - 1 ; i++) {
			packageClassName = packageClassName + "." + segs[i];
		}
		String classMethodSuffix = segs[segs.length - 1];
		String classMethod = classMethodSuffix.substring(0, classMethodSuffix.lastIndexOf("." + SUFFIX_VALUE_DEFAULT));
		String className = null;		//业务类名
		String methodName = null;		//方法名
		if(classMethod.indexOf("!") != -1) {
			String[] methodNamesArray = classMethod.split("!");
			className = methodNamesArray[0];
			methodName = methodNamesArray[1];
		} else {
			className = classMethod;
		}
		//格式化并构建Go类的类名
		className = StringUtil.upFirstChar(className) + StringUtil.upFirstChar(SUFFIX_VALUE_DEFAULT.toLowerCase());		//首字母大写
		packageClassName = packageClassName + "." + className;
		
		try {
			Class c = Class.forName(packageClassName);
			Method[] methods = c.getMethods();
			Object target = c.newInstance();
			
			//业务的Go类,支持继承BaseGo和为不继承BaseDao的两种方式
			if(target instanceof BaseGo) {		//如果该类继承了BaseGo父类
				Method method = c.getMethod(methodName);
				Method initMethod = c.getSuperclass().getMethod("initHttpServlet", HttpServletRequest.class, HttpServletResponse.class);
				//执行BaseGo初始化
				initMethod.invoke(target, httpRequest, httpResponse);
				//执行Go类的业务方法
				method.invoke(target);
			} else {		//不继承BaseGo父类的情况
				Method method = c.getMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);
				//执行Go类的业务方法
				method.invoke(target, httpRequest, httpResponse);
			}
			
		} catch (ClassNotFoundException e) {
			throw new GoNotFoundException("Go类:"+ packageClassName +"找不到", e);
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SecurityException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	} else {
		chain.doFilter(request, response);
	}
	
}

 

从上面的代码可看到，我们的业务BaseGo类支持两种形式，有不继承Go类的情况，如：

package org.mvcgo.action.school;

import java.io.IOException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class StudentGo {
	 
	public void add(HttpServletRequest request, HttpServletResponse response){
		System.out.println("student " + request.getQueryString());
	}
	
	public void save(HttpServletRequest request, HttpServletResponse response){
		String category = request.getParameter("category");
		System.out.println(category);
		response.sendRedirect("../test01.jsp");
	}

}

      上面的代码中，每个业务方法，都在ControllerFilter类中注入了HttpServletRequest和HttpServletResponse，这样，我们就可以方便地利用Servlet的API来处理我们网页请求了。

      为了实现更方便的Go编码，于是开发一个可重用的BaseGo类，代码如下：

package org.mvcgo.action;

import java.lang.reflect.Method;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.mvcgo.utils.ParameterFilter;

public class BaseGo {
	 
	protected HttpServletRequest request;
	protected HttpServletResponse response;

	public void initHttpServlet(HttpServletRequest request, HttpServletResponse response, Class clazz, Method method) {
		this.request = request;
		this.response = response;
	}
	
}

 

 这时，我们的StudentGo类，继承这个BaseGo，那些业务方法，可直接写成如下形式，而无须带参数。

public void add() throws IOException{
	System.out.println("student " + request.getQueryString());
}

public void save() throws IOException{
	String category = request.getParameter("category");
	System.out.println(category);
	response.sendRedirect("../test01.jsp");
}

 本例，运行服务器，在浏览器中访问时路径为

.../PROJECT_NAME(项目名)/school/student!add.go

.../PROJECT_NAME(项目名)/school/student!save.go

 

      本例小小的代码，无以跟Struts、WebWork待这些大框架比美，仅演示了在脱离大框架的情况下，用Servlet、Filter等原始的J2EE API开发Java Web项目时的一种方案，其中ControllerFilter、BaseGo等类都可继续开发扩充更多功能，以方便Web开发者的使用。