Highlight text from jdt java text editor using line numbers in eclipse plugin

Question

I am trying to write an eclipse plugin which highlights some text in java editor after user save the text (ResourceChangeListener). I am implementing ILightweightLabelDecorator and extending BaseLabelProvider , The method

public void decorate(Object arg0, IDecoration arg1)

getting called but I am getting Objects of type org.eclipse.jdt.internal.core.* eg org.eclipse.jdt.internal.core.PackageDeclaration. I need line numbers from that object so I can highlight that text. ASTNode object has a property to get the position (line numbers) but I am not getting that one. How can I get ASTNode from org.eclipse.jdt.internal.core.* objects?

Thanks in advance.

Answer 1

PackageDeclaration is part of the JDT Java Model which is a lighter weight version of the AST used by a lot of the Java code. As such it isn't related to ASTNode .

Many Java Model objects (including PackageDeclaration ) implement ISourceReference which tells you about the source code. This includes getSource and getSourceRange methods.

Answer 2

We can use the following method for accessing line number,

    private int getLineNumberInSource(SourceRefElement member) throws 
JavaModelException { 
    if (member == null || !member.exists()) { 
        return -1; 
    } 
    ICompilationUnit compilationUnit = member.getCompilationUnit(); 
    if (compilationUnit == null) { 
        return -1; 
    } 
    String fullSource = compilationUnit.getBuffer().getContents(); 
    if (fullSource == null) { 
        return -1; 
    } 
    ISourceRange nameRange = member.getNameRange(); 
    if (nameRange == null) { 
        return -1; 
    } 
    String string2 = fullSource.substring(0, nameRange.getOffset()); 
    return 
            string2.split(compilationUnit.findRecommendedLineSeparator()).length; 
}