Parsing a .java file

[Muhammad Ali]

I have this piece of code (it's a sample)

public class Ipv4 extends IpProt implements StructureInterface{

    private static final String name = "Ipv4";
    private static final String shortName = "Ipv4";
    private static final  String version="RFC 791, September 1981";

    private static final JapyField[] fieldList = {
        new BitField("version", 4),
        new BitField("ihl", 4),
        new Ipv4UByteField("tos"),
        new UShortField("len"),
        new UShortField("id"),
        new BitField("flags",3),
        new BitField("frag", 13),
        new UByteField("ttl"),
        new UByteField("proto"),
        new UShortField("chksum"),
        new Ipv4AddrField("src"),
        new Ipv4AddrField("dst"),
        new Ipv4OptionsField("options")       
    };   

    public Ipv4() {
        super(fieldList, name ,shortName);
        // TODO Auto-generated constructor stub
    }

    public  String getVersion()
    {
        return Ipv4.version;
    }
   
    public Structure generateInstance() {
        // TODO Auto-generated method stub
        return new Ipv4();
    }

    @Override
    public String getStructSummary(String out) throws JapyException,IOException{
        StringBuilder str = new StringBuilder(out);
        str.append(this.getShortName());
        str.append(":");
        str.append(String.format("s=%s",Ipv4AddrField.toString(this.gAS("src"))));
        str.append(String.format(",d=%s",Ipv4AddrField.toString(this.gAS("dst"))));
        return str.toString();
    }


}

What i need to do is to read this file as input and write an xml output file. which in this case would be

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<Ipv4>
    <version />
    <ihl />
    <tos />
    <len />
    <id />
    <flags />
    <frag />
    <ttl />
    <proto />
    <chksum />
    <src />
    <dst />
</Ipv4>

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Now, i have parsed and did the required job but i am not satisified with the implementation. I have read via InputReader and then match the hardcoded String to get the class name i.e there should be "class" keyword and "{" in the line and if it is true then i find the "className" in it. Now, what if the user has written the code as

public class className
{
    ...
}

My code will not get it's class name and hence will fail all over.

Now, what I was thinking

is there any api which reads the Java Files to get us better understanding? I was thinking about reflection API but in that case, i would not be able to read the lines which are in the fieldList array.

The second option could be using "Regular Expression". But i guess that would be more complex then

What should i do, any suggestions?

[Jeanne Boyarsky]

Muhammad,
An open source project like PMD reads in Java code very robustly. You could see how they do it.

[David Newton]

Your requirements are too vague to help effectively.

Your XML file contains only the elements in the fieldList array; creating XML from that is trivial and doesn't require any parsing at all-it just requires the ability to traverse the fieldList array and produce a suitable XML element for each type contained in the list.

If you *do* need to actually parse the Java file then use something like Antler or JavaCC or something, which are actual parsers. Unless your parsing needs are simplistic ("look for the fieldList value and grab everything in the following block) you do *not* want to parse Java by hand.

If you can be more specific regarding your actual needs and the conditions under which you must operate it'd be easier to provide input.