ServletContextImpl.java 文件源码

@Override
public FilterRegistration.Dynamic addFilter(final String filterName, final Filter filter) {
    ensureNotProgramaticListener();
    ensureNotInitialized();

    if (deploymentInfo.getFilters().containsKey(filterName)) {
        return null;
    }
    FilterInfo f = new FilterInfo(filterName, filter.getClass(), new ImmediateInstanceFactory<>(filter));
    deploymentInfo.addFilter(f);
    deployment.getFilters().addFilter(f);
    return new FilterRegistrationImpl(f, deployment, this);

}