how to handle nested exception

[Shantanu Deshmukh]

Hi,

I am trying to connect to mysql database. I am using try catch while establishing connection.
I want that I should be able to know what exception was caught, so that, I can show appropriate error message.
e.g if I pass incorrect hostname, i should show Wrong hostname provided.
One way to do is get class name of runtime exception class. but nested exception is being thrown like this..

There was some error while establishing connection to the databasecom.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception:

** BEGIN NESTED EXCEPTION **

java.net.UnknownHostException
MESSAGE: localhsost

STACKTRACE:

java.net.UnknownHostException: localhsost
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:867)
at java.net.InetAddress.getAddressFromNameService(InetAddress.java:1246)
at java.net.InetAddress.getAllByName0(InetAddress.java:1197)
at java.net.InetAddress.getAllByName(InetAddress.java:1128)
at java.net.InetAddress.getAllByName(InetAddress.java:1064)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:246)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:271)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2771)
at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:620)
at java.sql.DriverManager.getConnection(DriverManager.java:222)
at accessMySQL.accessMySQL.createConnection(accessMySQL.java:24)
at test.main(test.java:16)


** END NESTED EXCEPTION **



Last packet sent to the server was 1 ms ago.
Problem in establishing connection.

Now I would like to know that class name UnknownHostException, so I can setup a condition like

if(e.getClass().toString() == "UnknownHostException")
System.out.println("Exception caught while connection to database. Hostname appears to be incorrect");

please help !!

[Jan Cumps]

By fixing this typo: localhsost

[Darryl Burke]

Also see https://coderanch.com/t/548623/java/java/exact-exception-type

[Shantanu Deshmukh]

@jan cumps,

I did that typo deliberately. to get that exception. only to find out that it is throwing nested exception. i want to find out a way to get inner exception class name

[Philip Grove]

Use the getCause() method, if it returns null either the cause is non-existent or unknown. That method is actually inherited from Throwable so it should be usable for all Exceptions.

[Lalit Mehra]

i am not sure whether what i'm saying is right ...

java.net.UnknownHostException: localhsost

i found this in your first post ...

is the name "localhost" spelled correctly ...

[sze sze chan]

hummm....
are you trying to find what exception you getting after you input wrong host name ?

why don't you catch any exception then give it a invalid host name and e.tostring to print the exception name ?
for example

try{
your code
}catch(Exception e){
System.out.println("the exception is : " + e.toString());
}