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>