StreamTokenizer实例

最新推荐文章于 2024-07-31 14:09:16 发布

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本文详细解读了ArrayConverter类如何通过StreamTokenizer解析使用逗号分隔的数字数组，提供了深入理解Java类库实现细节的案例。

BeanUtils.copyProperty方法中用到的ArrayConverter类解析用逗号分隔的数字数组其中用到了StreamTokenizer类来看一下他的实现

package org.apache.commons.beanutils.converters;

public class ArrayConverter extends AbstractConverter {

    private List parseElements(Class type, String value) {

        if (log().isDebugEnabled()) {
            log().debug("Parsing elements, delimiter=[" + delimiter + "], value=[" + value + "]");
        }

        // Trim any matching '{' and '}' delimiters
        value = value.trim();
        if (value.startsWith("{") && value.endsWith("}")) {
            value = value.substring(1, value.length() - 1);
        }

        try {

            // Set up a StreamTokenizer on the characters in this String
            StreamTokenizer st = new StreamTokenizer(new StringReader(value));
            st.whitespaceChars(delimiter , delimiter); // Set the delimiters
            st.ordinaryChars('0', '9');  // Needed to turn off numeric flag
            st.wordChars('0', '9');      // Needed to make part of tokens
            for (int i = 0; i < allowedChars.length; i++) {
                st.ordinaryChars(allowedChars[i], allowedChars[i]);
                st.wordChars(allowedChars[i], allowedChars[i]);
            }

            // Split comma-delimited tokens into a List
            List list = null;
            while (true) {
                int ttype = st.nextToken();
                if ((ttype == StreamTokenizer.TT_WORD) || (ttype > 0)) {
                    if (st.sval != null) {
                        if (list == null) {
                            list = new ArrayList();
                        }
                        list.add(st.sval);
                    }
                } else if (ttype == StreamTokenizer.TT_EOF) {
                    break;
                } else {
                    throw new ConversionException("Encountered token of type "
                        + ttype + " parsing elements to '" + toString(type) + ".");
                }
            }

            if (list == null) {
                list = Collections.EMPTY_LIST;
            }
            if (log().isDebugEnabled()) {
                log().debug(list.size() + " elements parsed");
            }

            // Return the completed list
            return (list);

        } catch (IOException e) {

            throw new ConversionException("Error converting from String to '"
                    + toString(type) + "': " + e.getMessage(), e);

        }

    }

}