Sounds like a great solution Saul, thanks for figuring this out and
catching it early.
best regards,
Chris
Saul Farber wrote:
Hey all,
Just had a thought while looking through the SDE dummy jars.
Anywhere that one uses a construct like this:
public static final int TYPE_SMALLINT = 0;
For example, in SeColumnDefinition.java, I *think* java compiles the
value of a public static final <primitive> right into the code. I.e. if
there were two files like this:
public ClassA {
public static final int CONSTANT = 0;
}
and
public ClassA {
public static final int CONSTANT = 1;
}
And one compiled both of these class files into jars, and then compiled
the following program twice:
package org.depends.on.bad.java;
public ClassAUser {
public static void main(String[] args) {
if (ClassA.CONSTANT == 0)
System.out.println("ClassA.CONSTANT is Zero");
}
}
The above "if" statement is calculated at COMPILE-TIME, not runtime, and
so you'll get a fixed answer, no matter which ClassA you put on the
classpath. Here's some sample output:
[EMAIL PROTECTED] compilerTest $ javac -cp classAZERO.jar \
ClassAUser.java
[EMAIL PROTECTED] compilerTest $ java -cp classAZERO.jar:. \ ClassAUser
ClassA.CONSTANT is Zero
[EMAIL PROTECTED] compilerTest $ java -cp classAONE.jar:. \ ClassAUser
ClassA.CONSTANT is Zero
[EMAIL PROTECTED] compilerTest $
[EMAIL PROTECTED] compilerTest $
[EMAIL PROTECTED] compilerTest $ javac -cp classAONE.jar \
ClassAUser.java
[EMAIL PROTECTED] compilerTest $ java -cp classAZERO.jar:. \ ClassAUser
[EMAIL PROTECTED] compilerTest $ java -cp classAONE.jar:. \ ClassAUser
[EMAIL PROTECTED] compilerTest $
Hmmm...that's bad. This means that if we don't have the "public static
final int TYPE_SHAPE" set to exactly the same integer as the SDE API, we
won't be able to do drop-in replacement. Things will compile, but
anything based on a public constant (mostly shape type discovery and
such) won't work correctly unless one *compiles* the code with the SDE jars.
I wonder if I can get around this by changing the variables from public
static final to just "public static".
Then we might trick the compiler into not doing compile-time evaluation
of those constants.
Let me check...
Yes! It works.
Ok, so I'd suggest that we remove the "final" modifier from all the
public static constants in the SDE Java API dummy sources. Otherwise
stuff won't really work the way we want it to!
--saul
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The Open Planning Project
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