java 1.6 I want to create java POJO class dynamically

Question

I want to create java POJO class dynamically

Following is the requirment :

I have a method, which takes in parameters classname and a map .The map key will be the primitive type and map value will be the variable

create Class(String ClassName, HashMap map) 
{
}

When this method is invoked,it should create a .java file with the specified name and create the POJO with the passed hashmap and store it at some location.

Can you guys please help me with this.

I hope I could present my question clearly.

Thanks.

Answer 1

public class MapFirst
{
    public static void createClass (
        String className, Map <Class<?>, String> fields) throws IOException
    {
        StringBuilder builder = new StringBuilder ();

        String packageName;
        int idx = className.lastIndexOf ('.');
        if (idx >= 0)
        {
            packageName = className.substring (0, idx);
            className = className.substring (idx + 1);
        }
        else packageName = null;

        if (packageName != null)
            builder.append ("package ").append (packageName).append (";\n");

        builder.append ("\n");

        builder.append ("public class ").append (className).append ("\n");

        builder.append ("{\n");

        boolean flag = false;
        for (Map.Entry <Class <?>, String> field: fields.entrySet ())
        {
            Class <?> type = field.getKey ();
            String name = field.getValue ();
            String nameCapitalized = Character.toUpperCase (name.charAt (0)) + name.substring (1);

            if (flag) builder.append ("\n");
            flag = true;
            builder.append ("    private ").append (type).append (" ").append (name).append (";\n");
            builder.append ("\n");
            builder.append ("    public ").append (type).append (" get").append (nameCapitalized).append (" ()\n");
            builder.append ("    {\n");
            builder.append ("        return ").append (name).append (";\n");
            builder.append ("    }\n");
            builder.append ("\n");
            builder.append ("    public void set").append (nameCapitalized).append (" (").append (type).append (" ").append (name).append (")\n");
            builder.append ("    {\n");
            builder.append ("        this.").append (name).append (" = ").append (name).append (";\n");
            builder.append ("    }\n");
        }

        builder.append ("}\n");

        File dir = new File (
            packageName.replaceAll (
                "\\.",
                Matcher.quoteReplacement (System.getProperty ("file.separator"))));

        dir.mkdirs ();

        BufferedWriter writer = new BufferedWriter (
            new OutputStreamWriter (
                new FileOutputStream (
                    new File (dir, className + ".java"))));

        writer.write (builder.toString ());
        writer.close ();
    }

    public static void main (String [] args) throws Exception
    {
        Map <Class <?>, String> fields = new HashMap <Class<?>, String> ();
        fields.put (int.class, "foo");
        fields.put (double.class, "bar");
        createClass ("my.pkg.MyClass", fields);
    }
}