Log4j&Filter&Listener

日志管理

• 背景

日志記錄是應(yīng)用程序運(yùn)行中必不可少的一部分蚂维。具有良好格式和完備信息的日志記錄可以在程序出現(xiàn)問(wèn)題時(shí)幫助開(kāi)發(fā)人員迅速地定位錯(cuò)誤的根源

• Log4J的使用方法
  • 導(dǎo)入包log4j-1.2.17.jar
  • 在資源文件下面創(chuàng)建一個(gè)log4j.properties
  • 使用Java代碼實(shí)現(xiàn)日志的輸出

• 日志的級(jí)別

Log4J建議只使用四個(gè)級(jí)別刮萌，優(yōu)先級(jí)從高到低分別是ERROR宙搬、WARN斤贰、INFO、DEBUG

• 示例代碼

private static Logger logger = Logger.getLogger(ProductServlet.class)

protected void delete(HttpServletRequest req, HttpServletResponse resp) throws Exception {
  logger.debug("This is debug message.");
  logger.error("This is error message.");
  logger.info("This is info message.");
}

• log4j.properties(必須要確保文件被放到classes目錄下)

### \u8BBE\u7F6E###
log4j.rootLogger = debug,stdout,D,E

### \u8F93\u51FA\u4FE1\u606F\u5230\u63A7\u5236\u62AC ###
log4j.appender.stdout = org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target = System.out
log4j.appender.stdout.layout = org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern = [%-5p] %d{yyyy-MM-dd HH:mm:ss,SSS} method:%l%n%m%n

### \u8F93\u51FADEBUG \u7EA7\u522B\u4EE5\u4E0A\u7684\u65E5\u5FD7\u5230=E://logs/error.log ###
log4j.appender.D = org.apache.log4j.DailyRollingFileAppender
#log4j.appender.D.File = /logs/log.log
log4j.appender.D.Append = false
log4j.appender.D.Threshold = INFO 
log4j.appender.D.layout = org.apache.log4j.HTMLLayout
log4j.appender.D.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss}  [ %t:%r ] - [ %p ]  %m%n

### \u8F93\u51FAERROR \u7EA7\u522B\u4EE5\u4E0A\u7684\u65E5\u5FD7\u5230=E://logs/error.log ###
log4j.appender.E = org.apache.log4j.DailyRollingFileAppender
#log4j.appender.E.File =/logs/error.log 
log4j.appender.E.Append = false
log4j.appender.E.Threshold = ERROR 
log4j.appender.E.layout = org.apache.log4j.PatternLayout
log4j.appender.E.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss}  [ %t:%r ] - [ %p ]

過(guò)濾器概述

• WEB中的過(guò)濾器

WEB組件淆珊，在Java中最小的組件就是一個(gè)類（雙向）

• 特點(diǎn)

開(kāi)發(fā)人員可以實(shí)現(xiàn)用戶在訪問(wèn)某個(gè)目標(biāo)資源之前涮因，對(duì)訪問(wèn)的請(qǐng)求和響應(yīng)進(jìn)行攔截。

簡(jiǎn)單說(shuō)坷虑，就是可以實(shí)現(xiàn)Web容器對(duì)某個(gè)資源的訪問(wèn)前截獲進(jìn)行相關(guān)的處理甲馋，

還可以在某資源向Web容器返回響應(yīng)前進(jìn)行截獲處理

• Web中過(guò)濾器存在的意義
  • DRY不要重復(fù)自己
  • 責(zé)任分類:各自做自己擅長(zhǎng)的事兒

過(guò)濾器操作和應(yīng)用場(chǎng)景

實(shí)現(xiàn)Web容器對(duì)某資源的訪問(wèn)前截獲進(jìn)行相關(guān)處理，還可以在某資源向Web容器返回響應(yīng)前進(jìn)行截獲處理

• 過(guò)濾器能夠?qū)崿F(xiàn)的功能
  • 以常規(guī)的方式調(diào)用資源（訪問(wèn)servlet或JSP頁(yè)面）
  • 利用修改過(guò)的請(qǐng)求信息調(diào)用資源
  • 利用資源猖吴，但在發(fā)送響應(yīng)到瀏覽器之前對(duì)其進(jìn)行修改
  • 阻止該資源調(diào)用摔刁，取而代之的是跳轉(zhuǎn)到其他資源，返回一個(gè)特定的狀態(tài)碼

• 應(yīng)用場(chǎng)景
  • 可以對(duì)客戶提交的數(shù)據(jù)進(jìn)行重新編碼req.setCharacterEndocing("UTF-8");
  • 使用瀏覽器不緩存頁(yè)面的過(guò)濾器
  • 可以過(guò)濾掉客戶的非法文字
  • 驗(yàn)證客戶是否已經(jīng)登錄
  • 請(qǐng)求分發(fā)器(類似structs2)
  • 頁(yè)面?zhèn)戊o態(tài)化處理(.jsp結(jié)尾的變成.html結(jié)尾)

Filter開(kāi)發(fā)和使用

• Filter的開(kāi)發(fā)步驟
  • 創(chuàng)建一個(gè)類海蔽，實(shí)現(xiàn)Filter接口
  • 配置Filter(告訴Tomcat來(lái)管理Filter)

<filter>
  <filter-name>HelloFilter</filter-name>
  <filter-class>com.filter.HelloFilter</filter-class>
</filter>
<filter-mapping>
  <filter-name>HelloFilter</filter-name>
  <!-- 資源名稱共屈，指定要對(duì)那些資源進(jìn)行過(guò)濾 -->
  <url-pattern>/hello</url-pattern>
</filter-mapping>

Filter的細(xì)節(jié)處理

• 可以使用注解來(lái)配置Filter

但是使用注解來(lái)配置過(guò)濾器，就無(wú)法控制哪個(gè)過(guò)濾器先執(zhí)行

• FilterChain和FilterConfig

String getFilterName() // 獲取<filter-name>中的內(nèi)容
String getInitParameter(String name) // 獲取Filter中的初始化參數(shù),解決硬編碼
Enumeration getInitParameterNames() 
ServletContext getServletContext() // 獲取當(dāng)前應(yīng)用對(duì)象

• FilterCHain:過(guò)濾器鏈

注意:

對(duì)請(qǐng)求的攔截操作應(yīng)該在放行之前來(lái)實(shí)現(xiàn)

對(duì)響應(yīng)的攔截操作應(yīng)該在放行之后來(lái)實(shí)現(xiàn)

請(qǐng)求編碼過(guò)濾器

• 示例代碼

// 對(duì)請(qǐng)求參數(shù)的編碼進(jìn)行設(shè)置
public class CharacterEncodeingFilter implements Filter {
  // 編碼
  private String encoding;
  // 判斷是否要強(qiáng)制使用web.xml中的編碼配置
  private boolean force;
  
  public void init(FilterConfig filterConfig) throws ServletException {
    encoding = filterConfig.getInitParameter("encoding");
    force = Boolean.valueOf(filterConfig.getInitParameter("force"));
  }
  
  protected void doFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException {
    // 設(shè)置請(qǐng)求參數(shù)的編碼方式
    // 通常在程序中需要給編碼一個(gè)默認(rèn)值党窜，在絕大多數(shù)情況下拗引，我們不對(duì)其進(jìn)行配置
    if (request.getCharacterEncoding() == null || force && StringUtils.hasLength(encoding)) {
      request.setCharacterEncoding(encoding);
    } else {
      // 設(shè)置默認(rèn)碼
      request.setCharacterEncoding("UTF-8");
    }
    chain.doFilter(request, response);
  }
}

登錄驗(yàn)證過(guò)濾器CheckLoginFilter

• 示例代碼

LoginCheckFilter

public class LoginCheckFilter implements Filter {
  private String[] uris;
  private String contextPath;

  /**
   * Default constructor.
   */
  public LoginCheckFilter() {
      // 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;
      HttpServletResponse resp = (HttpServletResponse) response;

      // String uri = req.getRequestURI().substring(1);
      String uri = req.getRequestURI();

      if (Arrays.asList(uris).contains(uri)) {
          chain.doFilter(req, resp);
      } else {
          Object user = req.getSession().getAttribute("USER_IN_SESSION");
          if (user == null) {
              // 說(shuō)明沒(méi)有登錄
              resp.sendRedirect(req.getContextPath() + "/login.jsp");
              return;
          }
          chain.doFilter(req, resp);
      }
  }

  /**
   * @see Filter#init(FilterConfig)
   */
  public void init(FilterConfig fConfig) throws ServletException {
      // 獲取不需要驗(yàn)證的資源名稱
      // login.jsp,login,randomCode
      String notCheck = fConfig.getInitParameter("NOTCHECK");
      contextPath = fConfig.getInitParameter("contextPath");
      uris = notCheck.split(",");
      for (int i = 0; i < uris.length; i++) {
          uris[i] = contextPath + "/" + uris[i];
      }
  }
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    metadata-complete="false" version="3.0">

    <filter>
        <filter-name>CharacterEncodingFilter</filter-name>
        <filter-class>com._520.pps.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>utf-8</param-value>
        </init-param>
        <init-param>
            <param-name>force</param-name>
            <param-value>false</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>CharacterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <filter>
        <filter-name>LoginCheckFilter</filter-name>
        <filter-class>com._520.pps.web.filter.LoginCheckFilter</filter-class>
        <init-param>
            <param-name>NOTCHECK</param-name>
            <param-value>login.jsp,login,randomCode</param-value>
        </init-param>
        <init-param>
            <param-name>contextPath</param-name>
            <param-value>/log4j-filter-listener</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>LoginCheckFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

Listener(監(jiān)聽(tīng)器)

• 在JavaWeb中的監(jiān)聽(tīng)器(對(duì)作用域?qū)ο蟮谋O(jiān)聽(tīng))

// 作用域?qū)ο蟮谋O(jiān)聽(tīng)
// request--ServletRequestListener
void requestDestroyed(ServletRequestEvent sre);
void requestinitialized(ServletRequestEvent sre);

// session--HttpSessionListener
void sessionCreated(HttpSessionEvent se);
void sessionDestroyed(HttpSessionEvent se);

// application--ServletContextListener
void contextDestroyed(ServletContextEvent sce);
void contextInitalized(ServletContextEvent sce);

// 當(dāng)服務(wù)器啟動(dòng)的時(shí)候執(zhí)行該方法

• 在作用域中屬性監(jiān)聽(tīng)器(對(duì)作用域?qū)ο髮傩宰兓谋O(jiān)聽(tīng))

// ServletRequestAttributeListener
void attributeAdded(ServletRequestAttributeEvent srae);
void attributeRemoved(ServletRequestAttributeEvent srae);
void attributeReplaced(ServletRequestAttributeEvent srae);

// HttpSessionAttributeListener
void attributeAdded(HttpSessionBindingEvent se);
void attributeRemoved(HttpSessionBindingEvent se);
void attributeRepalced(HttpSessionBindingEvent se);

// ServletCOntextAttributeListener
void attributeAdded(ServletContextAttributeEvent scab);
void attributeRemoved(ServletContextAttributeEvent scab);
void attributeReplaced(ServletContextAttributeEvent scab);

• 注冊(cè)監(jiān)聽(tīng)器

<listener>
  <listener-class></listener-class>
</listener>

• 示例代碼

public class MySessionAttributeListener implements HttpSessionAttributeListener {
  @Override
  public void attributeAdded(HttpSessionBindingEvent se) {
    System.out.println("添加共享數(shù)據(jù)");
  }
  
  @Override
  public void attributeRemoved(HttpSessionBindingEvent se) {
    System.out.println("刪除共享數(shù)據(jù)");
  }
  
  @Override
  public void attributeReplaced(HttpSessionBindingEvent se) {
    System.out.println("修改共享數(shù)據(jù)");
  }
}