RestTemplate -- default timeout value
I think you can use SimpleClientHttpRequestFactory for timeout parameter. Instance of SimpleClientHttpRequestFactory can be set to rest template by constructor or setter method.
By default RestTemplate uses SimpleClientHttpRequestFactory so may be you can directly set value to restTemplate.
To explicitly answer the question...
The default timeout is infinite.
By default RestTemplate uses SimpleClientHttpRequestFactory and that in turn uses HttpURLConnection.
By default the timeout for HttpURLConnection is 0 - ie infinite, unless it has been set by these properties :
-Dsun.net.client.defaultConnectTimeout=TimeoutInMiliSec
-Dsun.net.client.defaultReadTimeout=TimeoutInMiliSec