jar URLs created using a context URL with our Handler point to the root of the jar rather than an entry

[wilkinsona]

When added to JarURLConnectionTests, this test will fail:

@Test
public void connectionToEntryInNestedJarFromUrlThatUsesExistingUrlAsContext()
        throws Exception {
    URL url = new URL(new URL("jar", null, -1,
            "file:" + getAbsolutePath() + "!/nested.jar!/", new Handler()), "/3.dat");
    JarFile nested = this.jarFile
            .getNestedJarFile(this.jarFile.getEntry("nested.jar"));
    assertThat(JarURLConnection.get(url, nested).getInputStream())
            .hasSameContentAs(new ByteArrayInputStream(new byte[] { 3 }));
}

Note that the Handler is a org.springframework.boot.loader.jar.Handler. If it is a sun.net.www.protocol.jar.Handler then the test passes. The key difference is what's returned from getFile() of the URL.

Handler	getFile()
Ours	/import.sql
JDK's	file:/Users/awilkinson/dev/spring/spring-boot/1.4.x/spring-boot-tools/spring-boot-loader/target/junit8413793381285871673/junit3981300331907567187.tmp!/nested.jar!/import.sql

This difference throws out the spec-related logic in JarURLConnection. The lack of a !/ leaves the JarURLConnection with an empty jarEntryName, i.e. pointing to the root of the nested jar. As a result, the attempt to get the input stream fails:

java.io.IOException: no entry name specified
    at org.springframework.boot.loader.jar.JarURLConnection.getInputStream(JarURLConnection.java:164)
    at org.springframework.boot.loader.jar.JarURLConnectionTests.connectionToEntryInNestedFromUrlThatUsesExistingUrlAsContext(JarURLConnectionTests.java:136)
    …

[wilkinsona]

Possible fix: https://github.com/wilkinsona/spring-boot/tree/gh-7021

@philwebb Could you please cast an eye over this one as well?

[snicoll]

@philwebb could you please put that review higher on your stack? If we manage to resolve this, #6983 is probably going to be a non-issue and we'll be able to remove the code we've added in 1.4.1 to workaround the fact that classpath: doesn't work with fat jars. Thanks!

[philwebb]

I think this is good, although it's pretty hard to be 100% confident. I've merged it.

[wilkinsona]

And… it broke stuff

[philwebb]

This was without doubt one of my most useless reviews ever. I knew I'd probably messed it up, but panicked because the issue had been open so long and committed it anyway. To make matters worse I did git commit --amend, you couldn't tell what had changed and it looked you were the author.

Sorry about that :(