Question

Take this HTTP query String:

foo=fooValue&bar=barValue&phleem=phleemValue

Or this one:

bar=barValue&phleem=phleemValue&foo=someOtherFoo

What would be the best way to remove the foo parameter?

All Java solutions welcome, but Guava preferred.

(There is no ServletContext available, so Servlet methods won’t help)

Update: The method should handle multiple parameters to remove.

Answer 1

This is not the most elegant solution, but works as you expect:

private String removeParameter(String string, final String parameterName) {
    List<String> list = newArrayList(string.split("&"));

    Collection<String> filtered = Collections2.filter(list, new Predicate<String>() {
        public boolean apply(String s) {
            return !s.startsWith(parameterName + "=");
        }
    });

    return Joiner.on("&").join(filtered);
}

UPDATE

To handle multiple parameters:

@Test
public void removesMultipleParametersFromQuery() throws Exception {
    String result = removeParameters("foo=fooValue&zee=lalal&bar=barValue&phleem=phleemValue", "foo", "bar");
    assertThat(result, is("zee=lalal&phleem=phleemValue"));
}

private String removeParameters(String query, final String...parameterNames) {
    List<String> list = newArrayList(query.split("&"));
    return Joiner.on("&").join(filter(list, startsWithAnyOf(parameterNames)));
}

private Predicate<String> startsWithAnyOf(final String[] parameterNames) {
    return new Predicate<String>() {
        public boolean apply(String s) {
            return !Iterables.any(newArrayList(parameterNames), isPrefixOf(s));
        }
    };
}

private Predicate<String> isPrefixOf(final String string){
    return new Predicate<String>() {
        public boolean apply(String candidate) {
            return string.startsWith(candidate);
        }
    };
}