副标题#e#
接下来我们来实现一个Filter
Filter.java接口
public interface Filter {
void doFilter(Request request, Response response, FilterChain chain) ;
}
FilterChain.java 关键的调用链
public class FilterChain implements Filter{
private List<Filter> filters = new ArrayList<>() ;
private int position = 0 ;
public void doFilter(Request request, Response response, FilterChain chain) {
if (position > filters.size() – 1) {
return ;
}
Filter filter = filters.get(this.position++) ;
filter.doFilter(request, response, this) ;
}
// 构建需要调用的Filter链
public FilterChain addFilter(Filter filter) {
this.filters.add(filter) ;
return this ;
}
}
Filter相关子类
public class LoginFilter implements Filter {
@Override
public void doFilter(Request request, Response response, FilterChain chain) {
System.out.println("LoginFilter entry…") ;
chain.doFilter(request, response, chain) ;
System.out.println("LoginFilter over…") ;
}
}
public class CharFilter implements Filter {
@Override
public void doFilter(Request request, Response response, FilterChain chain) {
System.out.println("CharFilter entry…") ;
chain.doFilter(request, response, chain) ;
System.out.println("CharFilter over…") ;
}
}
public class GrantFilter implements Filter {
@Override
public void doFilter(Request request, Response response, FilterChain chain) {
System.out.println("GrantFilter entry…") ;
chain.doFilter(request, response, chain) ;
System.out.println("GrantFilter over…") ;
}
}
客户端
public static void main(String[] args) {
LoginFilter loginFilter = new LoginFilter() ;
CharFilter charFilter = new CharFilter() ;
GrantFilter grantFilter = new GrantFilter() ;
FilterChain chain = new FilterChain() ;
chain.addFilter(loginFilter).addFilter(charFilter).addFilter(grantFilter) ;
Request request = new Request() ;
Response response = new Response() ;
chain.doFilter(request, response, null) ;
}
运行结果
#p#副标题#e#
按照添加Filter顺序，请求时先添加的先执行，返回时后添加的Filter先执行。java web中的Filter不也是这样么!!!