Servlet封装类

Servlet 提供了四个封装类：

public class ServletRequestWrapper extends java.lang.Object implements ServletRequest  //
public class ServletResponseWrapper extends java.lang.Object implements ServletResponse  //
public class HttpServletRequestWrapper extends ServletRequestWrapper implements HttpServletRequest  //
public class HttpServletResponseWrapper extends ServletResponseWrapper implements HttpServletResponse  // 

直接扩展这些封装类就可以修饰相应的的 request 和 response 对象了。

package app10a.filter;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

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;
import javax.servlet.http.HttpServletRequestWrapper;

@WebFilter(filterName = "AutoCorrectFilter", urlPatterns = { "/*" })
public class AutoCorrectFilter implements Filter {

    @Override
    public void destroy() {
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        AutoCorrectHttpServletRequestWrapper wrapper = new AutoCorrectHttpServletRequestWrapper(httpServletRequest);
        filterChain.doFilter(wrapper, response);
    }

    class AutoCorrectHttpServletRequestWrapper extends HttpServletRequestWrapper{  // 内部类
        private HttpServletRequest httpServletRequest;
        public AutoCorrectHttpServletRequestWrapper(HttpServletRequest httpServletRequest) {
            super(httpServletRequest);
            this.httpServletRequest = httpServletRequest;
        }
        @Override
        public String getParameter(String name) {
            return autoCorrect(httpServletRequest.getParameter(name));
        }
        @Override
        public String[] getParameterValues(String name) {
            return autoCorrect(httpServletRequest.getParameterValues(name));
        }
        @Override
        public Map<String, String[]> getParameterMap() {
            final Map<String, String[]> parameterMap = httpServletRequest.getParameterMap();
            Map<String, String[]> newMap = new Map<String, String[]>(){

                @Override
                public void clear() {
                    parameterMap.clear();
                }

                @Override
                public boolean containsKey(Object key) {
                    return parameterMap.containsKey(key);
                }

                @Override
                public boolean containsValue(Object value) {
                    return parameterMap.containsValue(value);
                }

                @Override
                public Set<Entry<String, String[]>> entrySet() {
                    return autoCorrect(parameterMap.entrySet());
                }

                @Override
                public String[] get(Object key) {
                    return autoCorrect(parameterMap.get(key));
                }

                @Override
                public boolean isEmpty() {
                    return parameterMap.isEmpty();
                }

                @Override
                public Set<String> keySet() {
                    return parameterMap.keySet();
                }

                @Override
                public String[] put(String key, String[] value) {
                    return parameterMap.put(key, value);
                }

                @Override
                public void putAll(Map<? extends String, ? extends String[]> map) {
                    parameterMap.putAll(map);
                }

                @Override
                public String[] remove(Object key) {
                    return parameterMap.remove(key);
                }

                @Override
                public int size() {
                    return parameterMap.size();
                }

                @Override
                public Collection<String[]> values() {
                    return autoCorrect(parameterMap.values());
                }

            };
            return newMap;
        }
    }
    private String autoCorrect(String value) {
        if (value == null) {
            return null;
        }
        value = value.trim();
        int length = value.length();
        StringBuilder temp = new StringBuilder();
        boolean lastCharWasSpace = false;
        for (int i = 0; i < length; i++) {
            char c = value.charAt(i);
            if (c == ' ') {
                if (!lastCharWasSpace) {
                    temp.append(c);
                }
                lastCharWasSpace = true;
            } else {
                temp.append(c);
                lastCharWasSpace = false;
            }
        }
        return temp.toString();
    }
    private String[] autoCorrect(String[] values) {
        if (values != null) {
            int length = values.length;
            for (int i = 0; i < length; i++) {
                values[i] = autoCorrect(values[i]);
            }
            return values;
        }
        return null;
    }
    private Collection<String[]> autoCorrect(Collection<String[]> valueCollection){
        Collection<String[]> newCollection = new ArrayList<String[]>();
        for (String[] values : newCollection) {
            newCollection.add(autoCorrect(values));
        }
        return newCollection;
    }
    private Set<Map.Entry<String, String[]>> autoCorrect(Set<Map.Entry<String, String[]>> entrySet){
        Set<Map.Entry<String, String[]>> newSet = new HashSet<Map.Entry<String, String[]>>();
        for (final Map.Entry<String, String[]> entry : entrySet) {
            Map.Entry<String, String[]> newEntry = new Map.Entry<String, String[]>(){

                @Override
                public String getKey() {
                    return entry.getKey();
                }

                @Override
                public String[] getValue() {
                    return autoCorrect(entry.getValue());
                }

                @Override
                public String[] setValue(String[] value) {
                    return entry.setValue(value);
                }
            };
            newSet.add(newEntry);
        }
        return newSet;
    }
}

<!-- test1.jsp -->
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>User Form</title>
</head>
<body>
    <form action="test2.jsp" method="post">
        <table>
            <tr>
                <td>Name: </td>
                <td><input type="text" name="name" /></td>
            </tr>
            <tr>
                <td>Address: </td>
                <td><input type="text" name="address" /></td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" value="Login"></td>
            </tr>
        </table>
    </form>
</body>
</html>

<!-- test2.jsp -->
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Form values</title>
</head>
<body>
    <table>
        <tr>
            <td>Name: </td>
            <td>${param.name } (length: ${fn:length(param.name) })</td>
        </tr>
        <tr>
            <td>Address: </td>
            <td>${param.address } (length:${fn:length(param.address) })</td>
        </tr>
    </table>
</body>
</html>