abstractconverter.java

APACHE 公司出的java bean 工具包

            } else {
                return null;
            }
        }
        return value;
    }

    /**
     * Handle Conversion Errors.
     * <p>
     * If a default value has been specified then it is returned
     * otherwise a ConversionException is thrown.
     *
     * @param type Data type to which this value should be converted.
     * @param value The input value to be converted
     * @param cause The exception thrown by the <code>convert</code> method
     * @return The default value.
     * @throws ConversionException if no default value has been
     * specified for this {@link Converter}.
     */
    protected Object handleError(Class type, Object value, Throwable cause) {
        if (log().isDebugEnabled()) {
            if (cause instanceof ConversionException) {
                log().debug("    Conversion threw ConversionException: " + cause.getMessage());
            } else {
                log().debug("    Conversion threw " + cause);
            }
        }

        if (useDefault) {
            return handleMissing(type);
        }

        ConversionException cex = null;
        if (cause instanceof ConversionException) {
            cex = (ConversionException)cause;
            if (log().isDebugEnabled()) {
                log().debug("    Re-throwing ConversionException: " + cex.getMessage());
                log().debug("    " + DEFAULT_CONFIG_MSG);
            }
        } else {
            String msg = "Error converting from '" + toString(value.getClass()) +
                    "' to '" + toString(type) + "' " + cause.getMessage();
            cex = new ConversionException(msg, cause);
            if (log().isDebugEnabled()) {
                log().debug("    Throwing ConversionException: " + msg);
                log().debug("    " + DEFAULT_CONFIG_MSG);
            }
            BeanUtils.initCause(cex, cause);
        }

        throw cex;

    }

    /**
     * Handle missing values.
     * <p>
     * If a default value has been specified then it is returned
     * otherwise a ConversionException is thrown.
     *
     * @param type Data type to which this value should be converted.
     * @return The default value.
     * @throws ConversionException if no default value has been
     * specified for this {@link Converter}.
     */
    protected Object handleMissing(Class type) {

        if (useDefault || type.equals(String.class)) {
            Object value = getDefault(type);
            if (useDefault && value != null && !(type.equals(value.getClass()))) {
                try {
                    value = convertToType(type, defaultValue);
                } catch (Throwable t) {
                    log().error("    Default conversion to " + toString(type)
                            + "failed: " + t);
                }
            }
            if (log().isDebugEnabled()) {
                log().debug("    Using default "
                        + (value == null ? "" : toString(value.getClass()) + " ")
                        + "value '" + defaultValue + "'");
            }
            return value;
        }

        ConversionException cex =  new ConversionException("No value specified for '" +
                toString(type) + "'");
        if (log().isDebugEnabled()) {
            log().debug("    Throwing ConversionException: " + cex.getMessage());
            log().debug("    " + DEFAULT_CONFIG_MSG);
        }
        throw cex;

    }

    /**
     * Set the default value, converting as required.
     * <p>
     * If the default value is different from the type the
     * <code>Converter</code> handles, it will be converted
     * to the handled type.
     *
     * @param defaultValue The default value to be returned
     * if the value to be converted is missing or an error
     * occurs converting the value.
     * @throws ConversionException if an error occurs converting
     * the default value
     */
    protected void setDefaultValue(Object defaultValue) {
        useDefault = false;
        if (log().isDebugEnabled()) {
            log().debug("Setting default value: " + defaultValue);
        }
        if (defaultValue == null) {
           this.defaultValue  = null;
        } else {
           this.defaultValue  = convert(getDefaultType(), defaultValue);
        }
        useDefault = true;
    }

    /**
     * Return the default type this <code>Converter</code> handles.
     *
     * @return The default type this <code>Converter</code> handles.
     */
    protected Class getDefaultType() {
        return defaultType;
    }

    /**
     * Return the default value for conversions to the specified
     * type.
     * @param type Data type to which this value should be converted.
     * @return The default value for the specified type.
     */
    protected Object getDefault(Class type) {
        if (type.equals(String.class)) {
            return null;
        } else {
            return defaultValue;
        }
    }
    
    /**
     * Provide a String representation of this converter.
     *
     * @return A String representation of this converter
     */
    public String toString() {
        return toString(getClass()) + "[UseDefault=" + useDefault + "]";
    }

    // ----------------------------------------------------------- Package Methods

    /**
     * Accessor method for Log instance.
     * <p>
     * The Log instance variable is transient and
     * accessing it through this method ensures it
     * is re-initialized when this instance is
     * de-serialized.
     *
     * @return The Log instance.
     */
    Log log() {
        if (log == null) {
            log = LogFactory.getLog(getClass());
        }
        return log;
    }

    /**
     * Change primitve Class types to the associated wrapper class.
     * @param type The class type to check.
     * @return The converted type.
     */
     Class primitive(Class type) {
        if (type == null || !type.isPrimitive()) {
            return type;
        }

        if (type == Integer.TYPE) {
            return Integer.class;
        } else if (type == Double.TYPE) {
            return Double.class;
        } else if (type == Long.TYPE) {
            return Long.class;
        } else if (type == Boolean.TYPE) {
            return Boolean.class;
        } else if (type == Float.TYPE) {
            return Float.class;
        } else if (type == Short.TYPE) {
            return Short.class;
        } else if (type == Byte.TYPE) {
            return Byte.class;
        } else if (type == Character.TYPE) {
            return Character.class;
        } else {
            return type;
        }
    }

    /**
     * Provide a String representation of a <code>java.lang.Class</code>.
     * @param type The <code>java.lang.Class</code>.
     * @return The String representation.
     */
    String toString(Class type) {
        String typeName = null;
        if (type == null) {
            typeName = "null";
        } else if (type.isArray()) {
            Class elementType = type.getComponentType();
            int count = 1;
            while (elementType.isArray()) {
                elementType = elementType .getComponentType();
                count++;
            }
            typeName = elementType.getName();
            for (int i = 0; i < count; i++) {
                typeName += "[]";
            }
        } else {
            typeName = type.getName();
        }
        if (typeName.startsWith("java.lang.") ||
            typeName.startsWith("java.util.") ||
            typeName.startsWith("java.math.")) {
            typeName = typeName.substring("java.lang.".length());
        } else if (typeName.startsWith(PACKAGE)) {
            typeName = typeName.substring(PACKAGE.length());
        }
        return typeName;
    }
}