public void setExpectedValue(final String expectedValue) {
        this.expectedValue = expectedValue;
        if (expectedValue != null) {
            pattern = Pattern.compile(expectedValue);
        }
    }
<p>Setter for the field <code>expectedValue</code>.</p>

@param expectedValue a {@link String} object
pac4j-core/src/main/java/org/pac4j/core/matching/matcher/HeaderMatcher.java