In Part 1 I described how you can use JavaCompiler's run() method to compile source code from a java.io.File. However the api also describes how you might extend the SimpleJavaFileObject class so you can compile source code from a string, rather than a physical file.
Since you can now compile code on-the-fly, you can easily use the CF code from part 1 to create their sample class: JavaSourceFromString.
<cfsavecontent variable="javaCode">
import javax.tools.SimpleJavaFileObject;
import java.net.URI;
/**
* A file object used to represent source coming from a string.
*/
public class JavaSourceFromString extends SimpleJavaFileObject {
/**
* The source code of this "file".
*/
final String code;
/**
* Constructs a new JavaSourceFromString.
* @param name the name of the compilation unit represented by this file object
* @param code the source code for the compilation unit represented by this file object
*/
public JavaSourceFromString(String name, String code) {
super(URI.create("string:///" + name.replace('.','/') + Kind.SOURCE.extension),
Kind.SOURCE);
this.code = code;
}
@Override
public CharSequence getCharContent(boolean ignoreEncodingErrors) {
return code;
}
}
</cfsavecontent>
<cfset pathToInputFile = "C:\myFiles\JavaSourceFromString.java" />
<cfset fileWrite(pathToInputFile, javaCode) />
However, instead of using the JavaLoader this time, we are going to output the class file directly to the WEB-INF\classes\ directory. That way the class will be automatically detected by ColdFusion. Now to redirect the output of the compiler, simply prepend the
-d <directory> flag to the list of sources passed into the compiler.
<!--- create a stream to capture errors --->
<cfset errStream = createObject("java", "java.io.ByteArrayOutputStream").init() />
<!--- get a compiler reference --->
<cfset provider = createObject("java", "javax.tools.ToolProvider") />
<cfset compiler = provider.getSystemJavaCompiler() />
<cfset args = [ "-d", "C:\ColdFusion8\wwwroot\WEB-INF\classes\", pathToInputFile ]>
<cfset status = compiler.run( javacast("null", ""),
javacast("null", ""),
errStream,
args
) />
<!--- display the status and any error messages --->
<!--- status: 0 == success --->
<cfset message = toString(errStream.toByteArray()) />
<cfset errStream.close() />
<b>COMPILER RESULTS:</b><hr />
<cfoutput>
STATUS: #status# (0 == success)<br />
ERRORS: #message# <br /><br />
</cfoutput>
Once the code is compiled, ColdFusion should automatically detect the new .class file in WEB-INF\classes\. So if everything went as planned, the new class should be ready to use right away, without rebooting the server.
(Note: If you make changes and compile the class a second time, ColdFusion will not automatically reload the class). Using the new class is very simple. Just create a new instance of
JavaSourceFromString, and pass in the name of your class and the source code as strings.
<cfsavecontent variable="javaCode">
import java.util.List;
import java.util.Vector;
public class MyClass
{
public static List<String> test() {
List<String> list = new Vector<String>();
list.add("Congratulations");
list.add("It worked");
return list;
}
}
</cfsavecontent>
<cfset SourceFromString = createObject("java", "JavaSourceFromString") />
<cfset fileObject = SourceFromString.init( "MyClass", javaCode) />
<cfset sourceList = [ fileObject ] />
Now to compile these sources, we are going to try something a little different: using a
CompilationTask. This option just provides some additional control over the compile process. We are also going to use a
DiagnosticCollector object, which provides an easy way to access error message details.
You can create a CompilationTask using the compiler's
getTask() method. Most of the arguments are the same as for the run() method. But there are two additional arguments:
options and classNames. The
options argument is just an array of settings you want to pass to the compiler. Such as the
-d flag used in the previous example. We are going to use that flag again to send the output to the WEB-INF\classes directory. Now to perform the actual compilation, use the call() method.
<cfset provider = createObject("java", "javax.tools.ToolProvider") />
<cfset compiler = provider.getSystemJavaCompiler() />
<cfset collector = createObject("java", "javax.tools.DiagnosticCollector").init() />
<cfset args = ["-d", "C:\ColdFusion8\wwwroot\WEB-INF\classes\" ]>
<cfset task = compiler.getTask( javacast("null", ""),
javacast("null", ""),
collector,
args,
javacast("null", ""),
sourceList
) />
<cfset status = task.call() />
To retrieve any error messages from the DiagnosticCollector, simply call the getDiagnostics() method. It returns an array of Diagnostic objects.
<cfset results = collector.getDiagnostics() />
COMPILER RESULTS:<hr />
<cfoutput>
STATUS: #status# (0 == success) <br />
<cfloop array="#results#" index="diagnostic">
Error on #diagnostic.getLineNumber()#
Starting at #diagnostic.getStartPosition()# <hr />
#diagnostic.getMessage(javacast("null", ""))# <br />
</cfloop>
<br />
</cfoutput>
All that is left is to test the compiled class. If everything went well, your results should look something like this. Ah, cfdump has never looked better ;)
COLDFUSION RESULTS:<hr />
<cfset myObj = createObject("java", "MyClass") />
<cfdump var="#myObj.test()#" label="MyClass.test();" />
As always comments/questions/corrections are welcome.
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