action="#{languageFrom.showChoice}": Target Unreachable, identifier 'languageFrom' resolved to null

package yingServlet;

import javax.faces.bean.ManagedBean; //记得不是import javax.annotation.ManagedBean;

@ManagedBean

public class LanguageForm {

private String language ;

public String getLanguage() {

return language;

}

public void setLanguage(String language) {

this.language = language.trim() ;

}

public String showChoice() {

if (isMissing(language)) {

return "missing-language" ;

}

else if (language.equalsIgnoreCase("Java")

|| language.equalsIgnoreCase("Groovy")) {

return "good-language" ;

}

else {

return "bad-language" ;

}

}

private boolean isMissing(String value) {

return (value == null) || value.trim().isEmpty() ;

}

}