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本文主要研究一下nacos client的ConfigFilterChainManager

IConfigFilterChain

nacos-1.1.3/api/src/main/java/com/alibaba/nacos/api/config/filter/IConfigFilterChain.java

public interface IConfigFilterChain {    /**     * Filter aciton     *     * @param request  request     * @param response response     * @throws NacosException NacosException     */    void doFilter(IConfigRequest request, IConfigResponse response) throws NacosException;}
  • IConfigFilterChain接口定义了doFilter方法

ConfigFilterChainManager

nacos-1.1.3/client/src/main/java/com/alibaba/nacos/client/config/filter/impl/ConfigFilterChainManager.java

public class ConfigFilterChainManager implements IConfigFilterChain {    private List<IConfigFilter> filters = Lists.newArrayList();    public synchronized ConfigFilterChainManager addFilter(IConfigFilter filter) {        // 根据order大小顺序插入        int i = 0;        while (i < this.filters.size()) {            IConfigFilter currentValue = this.filters.get(i);            if (currentValue.getFilterName().equals(filter.getFilterName())) {                break;            }            if (filter.getOrder() >= currentValue.getOrder() && i < this.filters.size()) {                i++;            } else {                this.filters.add(i, filter);                break;            }        }        if (i == this.filters.size()) {            this.filters.add(i, filter);        }        return this;    }    @Override    public void doFilter(IConfigRequest request, IConfigResponse response) throws NacosException {        new VirtualFilterChain(this.filters).doFilter(request, response);    }    //......}
  • ConfigFilterChainManager实现了IConfigFilterChain接口，其doFilter方法使用filters创建VirtualFilterChain，然后执行其doFilter方法；它提供了addFilter方法，可以根据filter的order顺序添加到filters中

VirtualFilterChain

nacos-1.1.3/client/src/main/java/com/alibaba/nacos/client/config/filter/impl/ConfigFilterChainManager.java

public class ConfigFilterChainManager implements IConfigFilterChain {    //......    private static class VirtualFilterChain implements IConfigFilterChain {        private final List<? extends IConfigFilter> additionalFilters;        private int currentPosition = 0;        public VirtualFilterChain(List<? extends IConfigFilter> additionalFilters) {            this.additionalFilters = additionalFilters;        }        @Override        public void doFilter(final IConfigRequest request, final IConfigResponse response) throws NacosException {            if (this.currentPosition != this.additionalFilters.size()) {                this.currentPosition++;                IConfigFilter nextFilter = this.additionalFilters.get(this.currentPosition - 1);                nextFilter.doFilter(request, response, this);            }        }    }    //......}
  • VirtualFilterChain实现了IConfigFilterChain接口，它维护了一个currentPosition属性，其doFilter方法会在currentPosition不等于additionalFilters.size()时递增currentPosition，然后取出nextFilter把自己作为参数去执行doFilter

IConfigFilter

nacos-1.1.3/api/src/main/java/com/alibaba/nacos/api/config/filter/IConfigFilter.java

public interface IConfigFilter {    /**     * Init     *     * @param filterConfig Filter Config     */    void init(IFilterConfig filterConfig);    /**     * do filter     *     * @param request     request     * @param response    response     * @param filterChain filter Chain     * @throws NacosException exception     */    void doFilter(IConfigRequest request, IConfigResponse response, IConfigFilterChain filterChain)            throws NacosException;    /**     * deploy     */    void deploy();    /**     * Get order     *     * @return order number     */    int getOrder();    /**     * Get filterName     *     * @return filter name     */    String getFilterName();}
  • IConfigFilter接口的doFilter方法的第三个参数为IConfigFilterChain；其实现类执行完自己的处理之后，如果要继续，可以执行filterChain.doFilter来继续交给下面的filter处理

小结

ConfigFilterChainManager实现了IConfigFilterChain接口，其doFilter方法使用filters创建VirtualFilterChain，然后执行其doFilter方法；它提供了addFilter方法，可以根据filter的order顺序添加到filters中

doc

  • ConfigFilterChainManager