PropertiesLoaderSupport should ignore socket/connect exceptions as well

[vinov]

Affects: 5.2.3-RELEASE
I am running on windows, trying to load properties from a shared network folder like \\remotehost\sharedfolder\common.properties, with ignoreResourceNotFound is set to true. If the property file is there, everything works, but in case the file is missing, loading fails with this somehow misleading exception:

java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method) ~[na:1.8.0_151]
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source) ~[na:1.8.0_151]
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source) ~[na:1.8.0_151]
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source) ~[na:1.8.0_151]
at java.net.AbstractPlainSocketImpl.connect(Unknown Source) ~[na:1.8.0_151]
at java.net.PlainSocketImpl.connect(Unknown Source) ~[na:1.8.0_151]
at java.net.Socket.connect(Unknown Source) ~[na:1.8.0_151]
at sun.net.ftp.impl.FtpClient.doConnect(Unknown Source) ~[na:1.8.0_151]
at sun.net.ftp.impl.FtpClient.tryConnect(Unknown Source) ~[na:1.8.0_151]
at sun.net.ftp.impl.FtpClient.connect(Unknown Source) ~[na:1.8.0_151]
at sun.net.ftp.impl.FtpClient.connect(Unknown Source) ~[na:1.8.0_151]
at sun.net.www.protocol.ftp.FtpURLConnection.connect(Unknown Source) ~[na:1.8.0_151]
at sun.net.www.protocol.ftp.FtpURLConnection.getInputStream(Unknown Source) ~[na:1.8.0_151]
at org.springframework.core.io.UrlResource.getInputStream(UrlResource.java:173) ~[spring-core-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.core.io.support.EncodedResource.getInputStream(EncodedResource.java:159) ~[spring-core-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.core.io.support.PropertiesLoaderUtils.fillProperties(PropertiesLoaderUtils.java:99) ~[spring-core-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.core.io.support.PropertiesLoaderSupport.loadProperties(PropertiesLoaderSupport.java:181) ~[spring-core-5.2.3.RELEASE.jar:5.2.3.RELEASE]

This error is very similar for example to this one in bitbucket issue. My simplistic view is, that ConnectException could be ignored, but I am not sure, what this change could break.

If adding ConnectException to the ignore list is not possible, PropertiesLoaderSupport could be made more flexible so we could override its behaviour. Now, all the important fields like locations are not accessible to an ancestor class as well as PropertiesLoaderUtils.fillProperties() is not visible. If the loader would like to be super user friendly, it would also allow somehow to set timeout on URLConnection through UrlResource.getInputStream().

[jhoeller]

Good point, and I would go as far as ignoring any SocketException (the superclass of ConnectException) in such a scenario since we only really want to let parsing exceptions through. I'll refine this for 5.2.9 (to be released next week).