filter的执行顺序
路由的filter可以配置多个。
如果是GatewayFilter,根据其在路由中的配置确定其执行顺序
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| spring:
cloud:
gateway:
routes:
- id: path_route
uri: http://www.baidu.com
predicates:
- Path=/get
filters:
- AddRequestHeader=X-Request-Foo, Bar
- AddResponseHeader=X-Response-Foo, Bar
- DedupeResponseHeader=Foo
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又因为一个请求分为进pre和出post两个方向。放在前面的filter在pre过程中先执行，在post过程中后执行。
然后再加上GlobalFilter，和GatewayFilter的顺序会怎么执行呢？
根据Ordered接口
我们自定义GlobalFilter时，都会同时实现Ordered接口。
他只有一个方法getOrder()，返回优先级。
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| @Bean
public GlobalFilter customFilter() {
return new CustomGlobalFilter();
}
public class CustomGlobalFilter implements GlobalFilter, Ordered {
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
log.info("custom global filter");
return chain.filter(exchange);
}
@Override
public int getOrder() {
return -1;
}
}
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数字越大，优先级越低，这个filter越靠后。
所以，源码中最高优先级的值就是Integer的最小值。
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/**
* Useful constant for the highest precedence value.
* @see java.lang.Integer#MIN_VALUE
*/
int HIGHEST_PRECEDENCE = Integer.MIN_VALUE;
/**
* Useful constant for the lowest precedence value.
* @see java.lang.Integer#MAX_VALUE
*/
int LOWEST_PRECEDENCE = Integer.MAX_VALUE;
|
做个测试
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| @Slf4j
@Configuration
public class GatewayTest {
@Bean
@Order(-1)
public GlobalFilter a() {
return (exchange, chain) -> {
log.info("first pre filter");
return chain.filter(exchange).then(Mono.fromRunnable(() -> {
log.info("third post filter");
}));
};
}
@Bean
@Order(0)
public GlobalFilter b() {
return (exchange, chain) -> {
log.info("second pre filter");
return chain.filter(exchange).then(Mono.fromRunnable(() -> {
log.info("second post filter");
}));
};
}
@Bean
@Order(1)
public GlobalFilter c() {
return (exchange, chain) -> {
log.info("third pre filter");
return chain.filter(exchange).then(Mono.fromRunnable(() -> {
log.info("first post filter");
}));
};
}
}
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触发一个请求，打印日志
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| first pre filter
second pre filter
third pre filter
first post filter
second post filter
third post filter
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也可以看出，“pre”类型的过滤器是在（exchanges,chain）->{}中执行的，
而“post”类型的过滤器是在chain.filter(exchange).then(Mono.fromRunnable(()->{}))中执行的。
以上代码，如果不喜欢lambda形式的写法，等价于以下写法
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| @Slf4j
@Component
public class CorsResponseHeaderFilter implements GlobalFilter, Ordered {
@Override
public int getOrder() {
return 1;
}
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
log.info("third pre filter");
return chain.filter(exchange).then(Mono.fromRunnable(() -> {
log.info("first post filter");
}));
}
|