spring cloud gateway 二次開發之動態路由注意事項

網關開發的過程中，因為有對某些服務進行動態的上下線的需求，所以進行了動態路由的開發，網上也有例子，實現方式就不贅述了，但這里有2個注意事項。

一路由信息里的斷言器信息不能為空

如果沒有傳斷言器信息，比如這樣

1
2
3
4
5
6
7

{
"id":"test",
"predicates":[],
"filters":[],
"uri":"lb://test",
"order":0
}

會拋出異常

1
2
3
4
5
6

reactor.core.Exceptions$ErrorCallbackNotImplemented: java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
Caused by: java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.rangeCheck(ArrayList.java:653)
at java.util.ArrayList.get(ArrayList.java:429)
at org.springframework.cloud.gateway.route.RouteDefinitionRouteLocator.combinePredicates(RouteDefinitionRouteLocator.java:221)
at org.springframework.cloud.gateway.route.RouteDefinitionRouteLocator.convertToRoute(RouteDefinitionRouteLocator.java:143)

我們看路由信息類的時候，可以發現斷言器是一個List，RouteDefinitionRouteLocator下邊有這個方法，會先取List中第一個斷言器，然后與之后的斷言器做組合，

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

private AsyncPredicate<ServerWebExchange> combinePredicates(
RouteDefinition routeDefinition) {
List<PredicateDefinition> predicates = routeDefinition.getPredicates();
//取出第一個斷言器
AsyncPredicate<ServerWebExchange> predicate = lookup(routeDefinition,
predicates.get(0));

//取出后續斷言器
for (PredicateDefinition andPredicate : predicates.subList(1,
predicates.size())) {
AsyncPredicate<ServerWebExchange> found = lookup(routeDefinition,
andPredicate);
//第一個斷言器和后續斷言器做 and 操作
predicate = predicate.and(found);
}

return predicate;
}

如果沒有填斷言器信息，就會報數組越界異常

二斷言器的名字不能隨便取

比如這里我取了一個 zuibuxing 的斷言器名字

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

{
"id":"test",
"predicates":[
{
"name":"zuibuxing",
"args":{
"_genkey_0":"/test/**"
}
}
],
"filters":[

],
"uri":"lb://test",
"order":0
}

會報這個錯誤

1
2
3
4
5

reactor.core.Exceptions$ErrorCallbackNotImplemented: java.lang.IllegalArgumentException: Unable to find RoutePredicateFactory with name zuibuxing
Caused by: java.lang.IllegalArgumentException: Unable to find RoutePredicateFactory with name zuibuxing
at org.springframework.cloud.gateway.route.RouteDefinitionRouteLocator.lookup(RouteDefinitionRouteLocator.java:240)
at org.springframework.cloud.gateway.route.RouteDefinitionRouteLocator.combinePredicates(RouteDefinitionRouteLocator.java:220)
at org.springframework.cloud.gateway.route.RouteDefinitionRouteLocator.convertToRoute(RouteDefinitionRouteLocator.java:143)

說找不到名字為 zuibuxing 的斷言器，這是因為保存自定義路由的時候，RouteDefinitionRouteLocato 會按照 name 去斷言器Map 里去尋找，

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

private final Map<String, RoutePredicateFactory> predicates = new LinkedHashMap<>();

... 中間代碼省略 ....

//按照名字尋找斷言器
private AsyncPredicate<ServerWebExchange> lookup(RouteDefinition route,
PredicateDefinition predicate) {
RoutePredicateFactory<Object> factory = this.predicates.get(predicate.getName());
if (factory == null) {
throw new IllegalArgumentException(
"Unable to find RoutePredicateFactory with name "
+ predicate.getName());
}

...以下代碼省略
}

RouteDefinitionRouteLocator 在這個Map中保存所有實現了 RoutePredicateFactory 的類,name是類名去掉RoutePredicateFactory，比如 AfterRoutePredicateFactory 斷言器的名字是 After，這里有兩個特殊的斷言器 CloudFoundryRouteService，ReadBodyPredicateFactory，因為它們的類名沒有以 RoutePredicateFactory 結尾，所以就用本身類名作為斷言器name
如果是隨便寫的，會導致找不到斷言器報錯，所以我們只能填gateway自己的斷言器，或者自己實現了 RoutePredicateFactory 的斷言器