name.martingeisse.wicket.util.WicketConverterUtil.java Source code

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Here is the source code for name.martingeisse.wicket.util.WicketConverterUtil.java

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/**
 * Copyright (c) 2011 Martin Geisse
 *
 * This file is distributed under the terms of the MIT license.
 */

package name.martingeisse.wicket.util;

import java.io.Serializable;
import name.martingeisse.common.util.string.StringUtil;
import org.apache.wicket.Component;
import org.apache.wicket.model.IModel;
import org.apache.wicket.model.Model;
import org.apache.wicket.util.convert.IConverter;

/**
 * Utility methods to deal with Wicket type converters.
 */
public class WicketConverterUtil {

    /**
     * Prevent instantiation.
     */
    private WicketConverterUtil() {
    }

    /**
     * Converts a value to a string. The type converter and locale are taken
     * from the specified context component. Null values are converted to the
     * empty string.
     * 
     * @param value the value to convert
     * @param context the context that provides the type converter and the locale
     * @return the converted value
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    public static String convertValueToString(Object value, Component context) {
        if (value == null) {
            return "";
        } else {
            IConverter converter = context.getConverter(value.getClass());
            return converter.convertToString(value, context.getLocale());
        }
    }

    /**
     * See {{@link #convertValueToString(Object, Component)} for a general
     * description of this method. This version also limits the length of the
     * output to the specified maximum number of characters.
     * 
     * @param value the value to convert
     * @param context the context that provides the type converter and the locale
     * @param maxLength the maximum length of the output string. Must be at
     * least 3 to allow for an ellipsis to be inserted.
     * @return the converted value
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    public static String convertValueToString(Object value, Component context, int maxLength) {
        return StringUtil.limitLength(convertValueToString(value, context), maxLength);
    }

    /**
     * Creates a model to be used with a label. If the value is {@link Serializable},
     * then it will be returned wrapped in a {@link Model}. Otherwise, a {@link Model}
     * is created with the value turned to a string using
     * {{@link #convertValueToString(Object, Component)}. This is also the reason
     * why this method is only useful with a label (or at least a component that
     * behaves like a label) -- other components have little use for a string instead
     * of the original value.
     * 
     * Note: there is no version of this method that accepts a maximum length.
     * Such a method would require to convert *all* values to string in advance, which
     * would increase session size dramatically. Use a custom label that limits
     * output length instead.
     * 
     * @param value the value
     * @param context the context component, used in case a string is needed
     * @return the model
     */
    public static IModel<?> createLabelModel(Object value, Component context) {
        if (value instanceof Serializable) {
            return Model.of((Serializable) value);
        } else {
            return Model.of(convertValueToString(value, context));
        }
    }

}