ServletContextImpl.java 文件源码

@Override
public FilterRegistration.Dynamic addFilter(final String filterName, final Class<? extends Filter> filterClass) {
    ensureNotProgramaticListener();
    ensureNotInitialized();
    if (deploymentInfo.getFilters().containsKey(filterName)) {
        return null;
    }
    FilterInfo filter = new FilterInfo(filterName, filterClass);
    deploymentInfo.addFilter(filter);
    deployment.getFilters().addFilter(filter);
    return new FilterRegistrationImpl(filter, deployment, this);
}