foreachsupport.java

来自「jakarta-taglibs」· Java 代码 · 共 401 行 · 第 1/2 页

        else if (o instanceof double[])
            items = toForEachIterator((double[]) o);
        else if (o instanceof Collection)
            items = toForEachIterator((Collection) o);
        else if (o instanceof Iterator)
            items = toForEachIterator((Iterator) o);
        else if (o instanceof Enumeration)
            items = toForEachIterator((Enumeration) o);
        else if (o instanceof Map)
            items = toForEachIterator((Map) o);
        /*
        else if (o instanceof ResultSet)
            items = toForEachIterator((ResultSet) o);
        */
        else if (o instanceof String)
            items = toForEachIterator((String) o);
        else
            items = toForEachIterator(o);

        return (items);
    }

    /*
     * Creates a ForEachIterator of Integers from 'begin' to 'end'
     * in support of cases where our tag handler isn't passed an
     * explicit collection over which to iterate.
     */
    private ForEachIterator beginEndForEachIterator() {
        /*
         * To plug into existing support, we need to keep 'begin', 'end',
         * and 'step' as they are.  So we'll simply create an Integer[]
         * from 0 to 'end', inclusive, and let the existing implementation
         * handle the subsetting and stepping operations.  (Other than
         * localizing the cost of creating this Integer[] to the start
         * of the operation instead of spreading it out over the lifetime
         * of the iteration, this implementation isn't worse than one that
         * created new Integers() as needed from next().  Such an adapter
         * to ForEachIterator could easily be written but, like I said,
         * wouldn't provide much benefit.)
         */
        Integer[] ia = new Integer[end + 1];
        for (int i = 0; i <= end; i++)
            ia[i] = new Integer(i);
        return new SimpleForEachIterator(Arrays.asList(ia).iterator());
    }


    //*********************************************************************
    // Private conversion methods to handle the various types we support

    // catch-all method whose invocation currently signals a 'matching error'
    protected ForEachIterator toForEachIterator(Object o)
            throws JspTagException {
        throw new JspTagException(Resources.getMessage("FOREACH_BAD_ITEMS"));
    }

    // returns an iterator over an Object array (via List)
    protected ForEachIterator toForEachIterator(Object[] a) {
        return new SimpleForEachIterator(Arrays.asList(a).iterator());
    }

    // returns an iterator over a boolean[] array, wrapping items in Boolean
    protected ForEachIterator toForEachIterator(boolean[] a) {
        Boolean[] wrapped = new Boolean[a.length];
        for (int i = 0; i < a.length; i++)
            wrapped[i] = new Boolean(a[i]);
        return new SimpleForEachIterator(Arrays.asList(wrapped).iterator());
    }

    // returns an iterator over a byte[] array, wrapping items in Byte
    protected ForEachIterator toForEachIterator(byte[] a) {
        Byte[] wrapped = new Byte[a.length];
        for (int i = 0; i < a.length; i++)
            wrapped[i] = new Byte(a[i]);
        return new SimpleForEachIterator(Arrays.asList(wrapped).iterator());
    }

    // returns an iterator over a char[] array, wrapping items in Character
    protected ForEachIterator toForEachIterator(char[] a) {
        Character[] wrapped = new Character[a.length];
        for (int i = 0; i < a.length; i++)
            wrapped[i] = new Character(a[i]);
        return new SimpleForEachIterator(Arrays.asList(wrapped).iterator());
    }

    // returns an iterator over a short[] array, wrapping items in Short
    protected ForEachIterator toForEachIterator(short[] a) {
        Short[] wrapped = new Short[a.length];
        for (int i = 0; i < a.length; i++)
            wrapped[i] = new Short(a[i]);
        return new SimpleForEachIterator(Arrays.asList(wrapped).iterator());
    }

    // returns an iterator over an int[] array, wrapping items in Integer
    protected ForEachIterator toForEachIterator(int[] a) {
        Integer[] wrapped = new Integer[a.length];
        for (int i = 0; i < a.length; i++)
            wrapped[i] = new Integer(a[i]);
        return new SimpleForEachIterator(Arrays.asList(wrapped).iterator());
    }

    // returns an iterator over a long[] array, wrapping items in Long
    protected ForEachIterator toForEachIterator(long[] a) {
        Long[] wrapped = new Long[a.length];
        for (int i = 0; i < a.length; i++)
            wrapped[i] = new Long(a[i]);
        return new SimpleForEachIterator(Arrays.asList(wrapped).iterator());
    }

    // returns an iterator over a float[] array, wrapping items in Float
    protected ForEachIterator toForEachIterator(float[] a) {
        Float[] wrapped = new Float[a.length];
        for (int i = 0; i < a.length; i++)
            wrapped[i] = new Float(a[i]);
        return new SimpleForEachIterator(Arrays.asList(wrapped).iterator());
    }

    // returns an iterator over a double[] array, wrapping items in Double
    protected ForEachIterator toForEachIterator(double[] a) {
        Double[] wrapped = new Double[a.length];
        for (int i = 0; i < a.length; i++)
            wrapped[i] = new Double(a[i]);
        return new SimpleForEachIterator(Arrays.asList(wrapped).iterator());
    }

    // retrieves an iterator from a Collection
    protected ForEachIterator toForEachIterator(Collection c) {
        return new SimpleForEachIterator(c.iterator());
    }

    // simply passes an Iterator through...
    protected ForEachIterator toForEachIterator(Iterator i) {
        return new SimpleForEachIterator(i);
    }

    // converts an Enumeration to an Iterator via a local adapter
    protected ForEachIterator toForEachIterator(Enumeration e) {

        // local adapter
        class EnumerationAdapter implements ForEachIterator {
            private Enumeration e;
            public EnumerationAdapter(Enumeration e) {
                this.e = e;
            }
            public boolean hasNext() {
                return e.hasMoreElements();
            }
            public Object next() {
                return e.nextElement();
            }
        }

        return new EnumerationAdapter(e);
    }

    // retrieves an iterator over the Map.Entry items in a Map
    protected ForEachIterator toForEachIterator(Map m) {
        return new SimpleForEachIterator(m.entrySet().iterator());
    }

    /* No more supported in JSTL. See interface Result instead.
    // thinly wraps a ResultSet in an appropriate Iterator
    protected ForEachIterator toForEachIterator(ResultSet rs)
            throws JspTagException {

        // local adapter
        class ResultSetAdapter implements ForEachIterator {
            private ResultSet rs;
            public ResultSetAdapter(ResultSet rs) {
                this.rs = rs;
            }
            public boolean hasNext() throws JspTagException {
                try {
                    return !(rs.isLast());      // dependent on JDBC 2.0
                } catch (java.sql.SQLException ex) {
                    throw new JspTagException(ex.getMessage());
                }
            }
            public Object next() throws JspTagException {
                try {
                    rs.next();
                    return rs;
                } catch (java.sql.SQLException ex) {
                    throw new JspTagException(ex.getMessage());
                }
            }
        }

        return new ResultSetAdapter(rs);
    }
    */

    // tokenizes a String as a CSV and returns an iterator over it
    protected ForEachIterator toForEachIterator(String s) {
        StringTokenizer st = new StringTokenizer(s, ",");
        return toForEachIterator(st);           // convert from Enumeration
    }

}