Idea使用Tomcat时Servlet找不到xml properties文件

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        Properties properties = new Properties();

        properties.load(new FileInputStream("a.properties"));

    }

如这段代码报错为:

java.io.FileNotFoundException: a.properties (系统找不到指定的文件。)

	at java.io.FileInputStream.open0(Native Method)

	at java.io.FileInputStream.open(FileInputStream.java:195)

	at java.io.FileInputStream.<init>(FileInputStream.java:138)

	at java.io.FileInputStream.<init>(FileInputStream.java:93)

	at Servlet1.doPost(Servlet1.java:16)

	at Servlet1.doGet(Servlet1.java:23)

	at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)

	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)

	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)

	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)

	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)

	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)

	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)

	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)

	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)

	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)

	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:409)

	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)

	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:754)

	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1376)

	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)

	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)

	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)

	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

	at java.lang.Thread.run(Thread.java:748)

a.properties此时无论放在resource目录下还是src根目录下都一样
------------------------------------------------------------------------------------------------------------------------------------------
然后，

System.getProperty("user.dir")

这段代码输出的路径为Tomcat的bin目录?????????
我只是一年没敲代码，发生了什么？？？？？？？？？？
没有使用Maven