转载自：https://blog.csdn.net/qq_30121245/article/details/52861935

1) 在项目中加入相应的包和类，加载那里无所谓，只要web.xml配置正确即可

package filters;

import java.io.IOException; 
import java.util.Enumeration;

import javax.servlet.*;

public final class PostDataDumperFilter implements Filter {

private FilterConfig filterConfig = null;

public void destroy() { 
this.filterConfig = null; 
}

public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException { 
if (filterConfig == null) 
return;

Enumeration names = request.getParameterNames(); 
StringBuffer output=new StringBuffer(); 
while (names.hasMoreElements()) { 
String name = (String) names.nextElement(); 
output.append(name+"="); 
String values[] = request.getParameterValues(name); 
for (int i = 0; i < values.length; i++) { 
if (i > 0) output.append("' "); 
output.append(values[i]); 
} 
if(names.hasMoreElements()) output.append("&"); 
} 
request.setAttribute("post", output); 
chain.doFilter(request, response); 
}

public void init(FilterConfig filterConfig) throws ServletException { 
this.filterConfig = filterConfig; 
} 
}

2) 配置web.xm，一般在路径 main/webapps/WEB-INF/web.xml: 
<filter> 
<filter-name>post-data-dumper-filter</filter-name> 
<filter-class>filters.PostDataDumperFilter</filter-class> 
</filter> 
<filter-mapping> 
<filter-name>post-data-dumper-filter</filter-name> 
<url-pattern>/*</url-pattern> 
</filter-mapping>

3) now you have the attribute postdata for each request and you can easily log it in access valve, for example:

<Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" 
                prefix="localhost_access_log." suffix=".txt" 
                pattern='%h %p %H %l %u %t "%r" params={%{post}r} %s %bbytes %Dms' resolveHosts="false"/>