spring框架中一个跟String的trim方法一样的方法

    @Test
    public void testTrimWhitespace() throws Exception {
        assertEquals(null, StringUtils.trimWhitespace(null));
        assertEquals("", StringUtils.trimWhitespace(""));
        assertEquals("", StringUtils.trimWhitespace(" "));
        assertEquals("", StringUtils.trimWhitespace("\t"));
        assertEquals("a", StringUtils.trimWhitespace(" a"));
        assertEquals("a", StringUtils.trimWhitespace("a "));
        assertEquals("a", StringUtils.trimWhitespace(" a "));
        assertEquals("a b", StringUtils.trimWhitespace(" a b "));
        assertEquals("a b  c", StringUtils.trimWhitespace(" a b  c "));
        assertEquals("a b  c", StringUtils.trimWhitespace("\r\f\n a b  c \t"));

    }

可以看到这个方法可以处理

\n 回车(\u000a)   
\t 水平制表符(\u0009)   
\r 换行(\u000d)   
\f 换页(\u000c)   

其实跟java的String方法的trim可以实现一样的功能

    /**
     * Trim leading and trailing whitespace from the given String.
     * @param str the String to check
     * @return the trimmed String
     * @see java.lang.Character#isWhitespace
     */
    public static String trimWhitespace(String str) {
        if (!hasLength(str)) {
            return str;
        }
        StringBuilder sb = new StringBuilder(str);
        while (sb.length() > 0 && Character.isWhitespace(sb.charAt(0))) {
            sb.deleteCharAt(0);
        }
        while (sb.length() > 0 && Character.isWhitespace(sb.charAt(sb.length() - 1))) {
            sb.deleteCharAt(sb.length() - 1);
        }
        return sb.toString();
    }

    /**
     * Check that the given String is neither {@code null} nor of length 0.
     * Note: Will return {@code true} for a String that purely consists of whitespace.
     * @param str the String to check (may be {@code null})
     * @return {@code true} if the String is not null and has length
     * @see #hasLength(CharSequence)
     */
    public static boolean hasLength(String str) {
        return hasLength((CharSequence) str);
    }

    /**
     * Check that the given CharSequence is neither {@code null} nor of length 0.
     * Note: Will return {@code true} for a CharSequence that purely consists of whitespace.
     * <p><pre class="code">
     * StringUtils.hasLength(null) = false
     * StringUtils.hasLength("") = false
     * StringUtils.hasLength(" ") = true
     * StringUtils.hasLength("Hello") = true
     * </pre>
     * @param str the CharSequence to check (may be {@code null})
     * @return {@code true} if the CharSequence is not null and has length
     * @see #hasText(String)
     */
    public static boolean hasLength(CharSequence str) {
        return (str != null && str.length() > 0);
    }