Struts学习第一课使用Filter作为控制器的MVC应用

MVC设计模式概览

实现MVC（Model,View,Controller）模式的应用程序由3大部分构成：

-模型：封装应用程序的数据和业务逻辑（POJO，Plain Old Java Object）

-视图，实现应用程序的信息显示功能（Jsp）

-控制器，接收来自用户的输入，调用模型层，，响应对应的视图组件Servlet，Filter。

下面看代码：

index.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
    <a href="product-input.action">Product Input</a>
</body>
</html>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>struts2-1</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>

input.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
    <form action="product-save.action" method="post">
    ProductName:<input type="text" name="productName">
    <br><br>
    ProductDesc:<input type="text" name="productDesc">
    <br><br>
    ProductPrice:<input type="text" name="productPrice">
    <br><br>
    <input type="submit" value="Submit">
    <br><br>
    </form>

</body>
</html>

package logan.struts.study;

import java.io.IOException;
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.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;

/**
 * Servlet Filter implementation class FilterDispatcher
 */
@WebFilter("*.action")
public class FilterDispatcher implements Filter {

    /**
     * Default constructor. 
     */
    public FilterDispatcher() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @see Filter#destroy()
     */
    public void destroy() {
        // TODO Auto-generated method stub
    }

    /**
     * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        
        HttpServletRequest req = (HttpServletRequest) request;
        
        //1.获取servletPath
        String servletPath = req.getServletPath();
        System.out.println(servletPath);
        //2.判断servletPath，若其等于"/product-input.action"则转发到
        ///WEB-INF/pages/input.jsp
        String path = null;
        if("/product-input.action".equals(servletPath)){
            path = "/WEB-INF/pages/input.jsp";
        }
        
        if(path != null){
            request.getRequestDispatcher(path).forward(request, response);
            return;
        }
        chain.doFilter(request, response);
    }

    /**
     * @see Filter#init(FilterConfig)
     */
    public void init(FilterConfig fConfig) throws ServletException {
        // TODO Auto-generated method stub
    }

}

在浏览器里面输入http://localhost:8080/struts2-1/product-input.action

可以看到

添加代码如下：

Product.java

package logan.struts.study;

public class Product {
    
    private Integer productId;
    private String productName;
    private String productDesc;
    
    private double productPrice;

    public Integer getProductId() {
        return productId;
    }

    public void setProductId(Integer productId) {
        this.productId = productId;
    }

    public String getProductName() {
        return productName;
    }

    public void setProductName(String productName) {
        this.productName = productName;
    }

    public String getProductDesc() {
        return productDesc;
    }

    public void setProductDesc(String productDesc) {
        this.productDesc = productDesc;
    }

    public double getProductPrice() {
        return productPrice;
    }

    public void setProductPrice(double productPrice) {
        this.productPrice = productPrice;
    }

    public Product(Integer productId, String productName, String productDesc, double productPrice) {
        super();
        this.productId = productId;
        this.productName = productName;
        this.productDesc = productDesc;
        this.productPrice = productPrice;
    }

    public Product() {
        
    }

    @Override
    public String toString() {
        return "Product [productId=" + productId + ", productName=" + productName + ", productDesc=" + productDesc
                + ", productPrice=" + productPrice + "]";
    }
}

package logan.struts.study;

import java.io.IOException;
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.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;

/**
 * Servlet Filter implementation class FilterDispatcher
 */
@WebFilter("*.action")
public class FilterDispatcher implements Filter {

    /**
     * Default constructor. 
     */
    public FilterDispatcher() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @see Filter#destroy()
     */
    public void destroy() {
        // TODO Auto-generated method stub
    }

    /**
     * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        
        HttpServletRequest req = (HttpServletRequest) request;
        
        //1.获取servletPath
        String servletPath = req.getServletPath();
        System.out.println(servletPath);
        //2.判断servletPath，若其等于"/product-input.action"则转发到
        ///WEB-INF/pages/input.jsp
        String path = null;
        if("/product-input.action".equals(servletPath)){
            path = "/WEB-INF/pages/input.jsp";
        }
        
        //3.若其等于"/product-save.action"则
        if("/product-save.action".equals(servletPath)){
            //1).获取请求参数
            String productName = request.getParameter("productName");
            String productDesc = request.getParameter("productDesc");
            String productPrice = request.getParameter("productPrice");
            
            
            //2).把请求信息封装为一个Product对象
            Product product = new Product(null, productName, productDesc, Double.parseDouble(productPrice));
            product.setProductId(1001);
            //3).执行保存操作
            System.out.println("Save Product" + product);
            
            //4).把Product对象保存到request中。${param.productName} -> ${requestScope.product.productName}
            request.setAttribute("product", product);
            path = "/WEB-INF/pages/details.jsp";
        }
        
        
        if(path != null){
            request.getRequestDispatcher(path).forward(request, response);
            return;
        }
        chain.doFilter(request, response);
    }

    /**
     * @see Filter#init(FilterConfig)
     */
    public void init(FilterConfig fConfig) throws ServletException {
        // TODO Auto-generated method stub
    }

}

details.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
        productId:${requestScope.product.productId }
        <br><br>
        productName:${requestScope.product.productName }
        <br><br>
        productDesc:${requestScope.product.productDesc }
        <br><br>
        productPrice:${requestScope.product.productPrice }
        <br><br>
</body>
</html>

当提交表单时

使用Filter作为控制器的好处：

使用一个过滤器来作为控制器，可以方便的在应用程序里对所有资源（包括静态资源）进行控制访问。

<url-pattern>*.action</url-pattern>

Servlet和Filter哪个更好？

Servlet能做的Filter都能做。

Filter能做的Servlet不一定能做，例如拦截资源。

Struts学习第一课 使用Filter作为控制器的MVC应用

Struts学习第一课使用Filter作为控制器的MVC应用