caused by

 

今天的问题是，

为什么有的异常信息是如此的简单，

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at Test.main(Test.java:85)

 

而有些问题的异常堆栈确实如此之多，看得人直晕直摇头：

java.io.IOException: Failed to retrieve RMIServer stub: javax.naming.ServiceUnavailableException [Root exception is java.rmi.ConnectException: Connection refused to host: 127.0.0.1; nested exception is: 
    java.net.ConnectException: Connection refused: connect]
    at javax.management.remote.rmi.RMIConnector.connect(RMIConnector.java:357)
    at javax.management.remote.JMXConnectorFactory.connect(JMXConnectorFactory.java:267)
    at javax.management.remote.JMXConnectorFactory.connect(JMXConnectorFactory.java:226)
    at jmx.Test.asfd(Test.java:68)
    at jmx.Test.main(Test.java:24)
Caused by: javax.naming.ServiceUnavailableException [Root exception is java.rmi.ConnectException: Connection refused to host: 127.0.0.1; nested exception is: 
    java.net.ConnectException: Connection refused: connect]
    at com.sun.jndi.rmi.registry.RegistryContext.lookup(RegistryContext.java:118)
    at com.sun.jndi.toolkit.url.GenericURLContext.lookup(GenericURLContext.java:203)
    at javax.naming.InitialContext.lookup(InitialContext.java:411)
    at javax.management.remote.rmi.RMIConnector.findRMIServerJNDI(RMIConnector.java:1924)
    at javax.management.remote.rmi.RMIConnector.findRMIServer(RMIConnector.java:1891)
    at javax.management.remote.rmi.RMIConnector.connect(RMIConnector.java:274)
    ... 4 more
Caused by: java.rmi.ConnectException: Connection refused to host: 127.0.0.1; nested exception is: 
    java.net.ConnectException: Connection refused: connect
    at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:619)
    at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:216)
    at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:202)
    at sun.rmi.server.UnicastRef.newCall(UnicastRef.java:340)
    at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
    at com.sun.jndi.rmi.registry.RegistryContext.lookup(RegistryContext.java:114)
    ... 9 more
Caused by: java.net.ConnectException: Connection refused: connect
    at java.net.DualStackPlainSocketImpl.connect0(Native Method)
    at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:69)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:157)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:391)
    at java.net.Socket.connect(Socket.java:579)
    at java.net.Socket.connect(Socket.java:528)
    at java.net.Socket.<init>(Socket.java:425)
    at java.net.Socket.<init>(Socket.java:208)
    at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:40)
    at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:146)
    at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:613)
    ... 14 more

（这个例子的异常信息相对大家见过的应该不算什么）

 

当然。其实这个地球人都知道， 复杂性不一样。

 

今天的挑战是，什么情况下回出现 caused by、 root cause/exception is: 这样的语句？