一、现象描述
通过ftp客户端代码登录ftp服务器向指定目录发布文件，发生FTPException异常，消息提示“Maximum login limit has been reached”，详情如下：
_, ftpserver0_.CREATE_TIME as CREATE8_12_0_, ftpserver0_.UPDATE_TIME as UPDATE9_@b@12_0_, ftpserver0_.STATUS as STATUS12_0_, ftpserver0_.VIRTUAL_DIR as VIRTUAL11_1@b@2_0_ from FTPSERVER ftpserver0_ where ftpserver0_.ID=?@b@[INFO ][2015-12-20 21:56:26][com.xwood.pms.core.ftp.IssFTPClient.login(IssFTPClien@b@t.java:74)]:建立连接@b@it.sauronsoftware.ftp4j.FTPException [code=421, message= Maximum login limit has@b@ been reached.]@b@ at it.sauronsoftware.ftp4j.FTPClient.login(FTPClient.java:1242)@b@ at it.sauronsoftware.ftp4j.FTPClient.login(FTPClient.java:1168)@b@ at com.xwood.pms.core.ftp.IssFTPClient.login(IssFTPClient.java:82)@b@ at com.xwood.pms.util.publisher.FtpOms.upload(FtpOms.java:171)@b@ at com.xwood.pms.util.publisher.FtpOms.upload(FtpOms.java:144)@b@ at com.xwood.pms.service.impl.FilePublisher.createAndPublishWithMultiPorta@b@ls(FilePublisher.java:306)@b@ at com.xwood.pms.util.publisher.PublishRunnable.call(PublishRunnable.java:@b@59)@b@ at com.xwood.pms.util.publisher.PublishRunnable.call(PublishRunnable.java:@b@1)@b@ at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)@b@ at java.util.concurrent.FutureTask.run(Unknown Source)@b@ at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source@b@)@b@ at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)@b@ at java.lang.Thread.run(Unknown Source)@b@[INFO ][2015-12-20 21:56:26][com.xwood.pms.core.ftp.IssFTPClient.login(IssFTPClien@b@t.java:87)]:登录FTP服务器失败！Maximum login limit has been reached.@b@java.lang.IllegalStateException: Client not authenticated@b@ at it.sauronsoftware.ftp4j.FTPClient.changeDirectory(FTPClient.java:1610@b@)@b@ at com.xwood.pms.core.ftp.IssFTPClient.changeDirectory(IssFTPClient.java:2@b@04)@b@ at com.xwood.pms.util.publisher.FtpOms.upload(FtpOms.java:172)@b@ at com.xwood.pms.util.publisher.FtpOms.upload(FtpOms.java:144)@b@ at com.xwood.pms.service.impl.FilePublisher.createAndPublishWithMultiPorta@b@ls(FilePublisher.java:306)@b@ at com.xwood.pms.util.publisher.PublishRunnable.call(PublishRunnable.java:@b@59)@b@ at com.xwood.pms.util.publisher.PublishRunnable.call(PublishRunnable.java:@b@1)@b@ at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)@b@ at java.util.concurrent.FutureTask.run(Unknown Source)@b@ at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source@b@)@b@ at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)@b@ at java.lang.Thread.run(Unknown Source)@b@com.xwood.pms.core.freemarker.exception.FtpException: ftp异常！file:/_site_domain_@b@/_root/5870/5930/5931/6189/6515//E:/SaaServices/tomcat6-exe/webapps/ROOT/_root/5@b@870/5930/5931/6189/6515/index.htmlClient not authenticated@b@ at com.xwood.pms.util.publisher.FtpOms.upload(FtpOms.java:188)@b@ at com.xwood.pms.util.publisher.FtpOms.upload(FtpOms.java:144)@b@ at com.xwood.pms.service.impl.FilePublisher.createAndPublishWithMultiPorta@b@ls(FilePublisher.java:306)
二、解决步骤
1. 从FTPException异常消息很明显，是因ftp客户端登陆数超上限造成的，所以需将ftp服务器的登录数限制配置参数调大
2. 这边是用的 apache-ftpserver-1.0.6 （如是其他服务器如vsftpd、ServU请修改其配置），启动命令是通过ftpd-typical.xml的xml配置参数进行初始化ftpserver对象
3. 通过ftp默认启动,定位根目录common -> lib -> f tpserver-core-1.0.6.jar包文件
4. 通过源码查找最大登录数相关配置文件及属性（max-logins最大登录数），找到如下图所示
5. 找到ftpd-typical.xml初始化配置文件，配置了如下箭头所示属性（max-logins="999999"）
<server xmlns="http://mina.apache.org/ftpserver/spring/v1"@b@ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"@b@ xsi:schemaLocation="@b@ http://mina.apache.org/ftpserver/spring/v1 http://mina.apache.org/ftpserver/ftpserver-1.0.xsd @b@ "@b@ id="myServer" max-logins="999999" max-threads="9999">@b@ <listeners>@b@ <nio-listener name="default" port="21">@b@ <ssl>@b@ <keystore file="./res/ftpserver.jks" password="password" />@b@ </ssl>@b@ </nio-listener>@b@ </listeners>@b@ <file-user-manager file="./res/conf/users.properties" encrypt-passwords = "clear" />@b@</server>
6. 重启服务，一切正常