【小家Spring】从OncePerRequestFilter的源码解读去了解Spring内置的Filter的特别之处以及常见过滤器使用介绍（中）

  <!-- characterEncodingFilter字符编码过滤器 -->
  <filter>
    <filter-name>characterEncodingFilter</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
      <!--要使用的字符集，一般我们使用UTF-8(保险起见UTF-8最好)-->
      <param-name>encoding</param-name>
      <param-value>UTF-8</param-value>
    </init-param>
    <init-param>
      <!--是否强制设置request的编码为encoding，默认false，不建议更改-->
      <param-name>forceRequestEncoding</param-name>
      <param-value>false</param-value>
    </init-param>
    <init-param>
      <!--是否强制设置response的编码为encoding，建议设置为true，下面有关于这个参数的解释-->
      <param-name>forceResponseEncoding</param-name>
      <param-value>true</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>characterEncodingFilter</filter-name>
    <!--这里不能留空或者直接写 ' / ' ，否者不起作用-->
    <url-pattern>/*</url-pattern>
  </filter-mapping>

<Connector port="8080" protocol="HTTP/1.1" 
           connectionTimeout="20000"
           redirectPort="8443"
           parseBodyMethods="POST,PUT,DELETE"
           URIEncoding="UTF-8" />

    <filter>
        <filter-name>httpPutFormContentFilter</filter-name>
        <filter-class>org.springframework.web.filter.HttpPutFormContentFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>httpPutFormContentFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

private static class FormContentRequestWrapper extends HttpServletRequestWrapper { ... }

  @Override
  protected boolean shouldLog(HttpServletRequest request) {
    return logger.isDebugEnabled();
  }
  @Override
  protected void beforeRequest(HttpServletRequest request, String message) {
    logger.debug(message);
  }
  @Override
  protected void afterRequest(HttpServletRequest request, String message) {
    logger.debug(message);
  }

  @Override
  protected void beforeRequest(HttpServletRequest request, String message) {
    getServletContext().log(message);
  }
  @Override
  protected void afterRequest(HttpServletRequest request, String message) {
    getServletContext().log(message);
  }

public static final String DEFAULT_BEFORE_MESSAGE_PREFIX = "Before request [";
public static final String DEFAULT_BEFORE_MESSAGE_SUFFIX = "]";
public static final String DEFAULT_AFTER_MESSAGE_PREFIX = "After request [";
public static final String DEFAULT_AFTER_MESSAGE_SUFFIX = "]";
// 默认body体里只会打印出50个字符，自己可以自定义修改
private static final int DEFAULT_MAX_PAYLOAD_LENGTH = 50;
//true表示包含查询参数  形如：[  uri=xxx?a=xx&b=xxx  ]
private boolean includeQueryString = false;
//true表示包含客户端相关信息
private boolean includeClientInfo = false;
//true表示包含请求头信息
private boolean includeHeaders = false;
//true表示包含body体性息
private boolean includePayload = false;

  public void setMaxPayloadLength(int maxPayloadLength) {
    Assert.isTrue(maxPayloadLength >= 0, "'maxPayloadLength' should be larger than or equal to 0");
    this.maxPayloadLength = maxPayloadLength;
  }
  //自定义请求前、后的前缀、后缀等等  这个其实是建议定制的  个性化点比较好
  public void setBeforeMessagePrefix(String beforeMessagePrefix) {
    this.beforeMessagePrefix = beforeMessagePrefix;
  }
  //是否过滤异步的请求  这里false表示要过滤
  @Override
  protected boolean shouldNotFilterAsyncDispatch() {
    return false;
  }
  //生成日志消息的方法  这个强烈不建议调用者自己去做（当然，你要个性化，你随意）  getMessagePayload
  protected String createMessage(HttpServletRequest request, String prefix, String suffix) { ... }
  //这个非常的重要，判断哪些请求输出日志，哪些不需要输出。比如get请求，我们一般都不需要输出日志的 (至于能够实现标注指定注解接口采取输出日志呢？这个就做不到了，因为还没有到方法呢，没有办法拿到方法元信息)  但是若通过HandlerInterceptor来拦截，是可以处理方法注解的
  protected boolean shouldLog(HttpServletRequest request) {
    return true;
  }
  //在系统默认的message的基础上，你自己再去个性化吧。或者不用此message变量都成~  比如自己可以计算出请求耗时~
  protected abstract void beforeRequest(HttpServletRequest request, String message);
  protected abstract void afterRequest(HttpServletRequest request, String message);