jpa报错 Unable to acquire a connection from driver [null], user [null] and URL [null] 为啥报错 因为你在persistence.xml中没配置你数据库的相应信息 咋解决 persistence.xml在哪里? 咋编辑这东西? 咋配置 <?xml version="1.0" encoding="UTF-8"?> <persistence version="2.…
Eclipse报错 due to restriction on required library C:/Java/jdk1.6.0_10/jre/lib/rt.jar 解决方案 Eclipse 编译时报错: Access restriction:The type NEW is not accessible due to restriction on required library C:/Java/jdk1.6.0_10/jre/lib/rt.jar 解决方法如下: 1.进入Project -…
linux 下通过xhost进入图形界面,经常会出现报错“unable to open display” linux下的操作步骤如下: [root@localhost ~]# vncserver New 'localhost:1 (root)' desktop is localhost:1 Starting applications specified in /root/.vnc/xstartupLog file is /root/.vnc/localhost:1.log [root@loca…
xhprof查看性能测试图一直报错:failed to execute cmd: ” dot -Tpng”多种因素解决方案最近在新环境进行php代码性能测试,用了xhprof这个工具,搭建好以后,点击[View Full Callgraph]查看性能分析图链接一直报错:failed to execute cmd: ” dot -Tpng” 原因一:未安装graphviz如果看到 sh: dot: command not found ,说明服务器上没有安装画图软件graphviz 2.yum安装:…