Error using List as @RequestParam

[Juchar]

• Framework version: 1.1
• Implementations: Spring Boot

Scenario

Using List<T> as a @RequestParam and executing the request /test?list=1,2,3.

Expected behavior

Executing the request locally by starting Spring Boot the list is filled correctly.

Actual behavior

An exception occurs.

Steps to reproduce

Implement the following method in a controller:

@RequestMapping(path = "test", produces = MediaType.APPLICATION_JSON_VALUE)
public String test(List<String> list) {}

sam.yml:

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: My Description
Resources:
  MyServiceFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: com.example.StreamLambdaHandler::handleRequest
      Runtime: java8
      CodeUri: target/example.jar
      MemorySize: 512
      Policies: AWSLambdaBasicExecutionRole
      Timeout: 30
      Events:
        GetResource:
          Type: Api
          Properties:
            Path: /{proxy+}
            Method: GET

Outputs:
  ExampleAPI:
    Description: URL for application
    Value: !Sub 'https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/test'
    Export:
      Name: ExampleAPI

Execute:
/test?list=1,2,3 or /test?list=1&list=2&list=3 on the Lambda URL.

Full log output

2018-06-21 05:24:28.706 ERROR 1 --- [ main] o.s.boot.web.support.ErrorPageFilter : Forwarding to error page from request [/test] due to exception [Failed to instantiate [java.util.List]: Specified class is an interface]
org.springframework.beans.BeanInstantiationException: Failed to instantiate [java.util.List]: Specified class is an interface
at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:99) ~[task/:na]
at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.createAttribute(ModelAttributeMethodProcessor.java:141) ~[task/:na]
at org.springframework.web.servlet.mvc.method.annotation.ServletModelAttributeMethodProcessor.createAttribute(ServletModelAttributeMethodProcessor.java:81) ~[task/:na]
at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.resolveArgument(ModelAttributeMethodProcessor.java:101) ~[task/:na]
at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121) ~[task/:na]
at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:158) ~[task/:na]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:128) ~[task/:na]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97) ~[task/:na]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) ~[task/:na]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) ~[task/:na]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[task/:na]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967) ~[task/:na]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901) ~[task/:na]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) ~[task/:na]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) ~[task/:na]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:687) ~[task/:na]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) ~[task/:na]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) ~[task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.FilterChainManager$ServletExecutionFilter.doFilter(FilterChainManager.java:351) ~[task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.FilterChainHolder.doFilter(FilterChainHolder.java:84) [task/:na]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[task/:na]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.FilterChainHolder.doFilter(FilterChainHolder.java:84) [task/:na]
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105) ~[task/:na]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.FilterChainHolder.doFilter(FilterChainHolder.java:84) [task/:na]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81) ~[task/:na]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.FilterChainHolder.doFilter(FilterChainHolder.java:84) [task/:na]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) ~[task/:na]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.FilterChainHolder.doFilter(FilterChainHolder.java:84) [task/:na]
at org.springframework.boot.web.support.ErrorPageFilter.doFilter(ErrorPageFilter.java:115) [task/:na]
at org.springframework.boot.web.support.ErrorPageFilter.access$000(ErrorPageFilter.java:59) [task/:na]
at org.springframework.boot.web.support.ErrorPageFilter$1.doFilterInternal(ErrorPageFilter.java:90) [task/:na]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [task/:na]
at org.springframework.boot.web.support.ErrorPageFilter.doFilter(ErrorPageFilter.java:108) [task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.FilterChainHolder.doFilter(FilterChainHolder.java:84) [task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.AwsLambdaServletContainerHandler.doFilter(AwsLambdaServletContainerHandler.java:207) [task/:na]
at com.amazonaws.serverless.proxy.spring.SpringBootLambdaContainerHandler.handleRequest(SpringBootLambdaContainerHandler.java:154) [task/:na]
at com.amazonaws.serverless.proxy.spring.SpringBootLambdaContainerHandler.handleRequest(SpringBootLambdaContainerHandler.java:52) [task/:na]
at com.amazonaws.serverless.proxy.internal.LambdaContainerHandler.proxy(LambdaContainerHandler.java:168) [task/:na]
at com.amazonaws.serverless.proxy.internal.LambdaContainerHandler.proxyStream(LambdaContainerHandler.java:200) [task/:na]
at com.example.StreamLambdaHandler.handleRequest(StreamLambdaHandler.java:30) [task/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_141]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_141]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_141]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_141]
at lambdainternal.EventHandlerLoader$StreamMethodRequestHandler.handleRequest(EventHandlerLoader.java:350) [LambdaSandboxJava-1.0.jar:na]
at lambdainternal.EventHandlerLoader$2.call(EventHandlerLoader.java:888) [LambdaSandboxJava-1.0.jar:na]
at lambdainternal.AWSLambda.startRuntime(AWSLambda.java:283) [LambdaSandboxJava-1.0.jar:na]
at lambdainternal.AWSLambda.<clinit>(AWSLambda.java:64) [LambdaSandboxJava-1.0.jar:na]
at java.lang.Class.forName0(Native Method) [na:1.8.0_141]
at java.lang.Class.forName(Class.java:348) [na:1.8.0_141]
at lambdainternal.LambdaRTEntry.main(LambdaRTEntry.java:94) [LambdaJavaRTEntry-1.0.jar:na]

[sapessi]

Hey @Juchar, the exception thrown says that Spring cannot instantiate a List - rightly so, because List is an interface. Have you tried declaring the parameter as an implementation of List? For example ArrayList?

[Juchar]

@sapessi
Hey, that was my intention too, so I debugged a little bit further. Adding @RequestParam to the parameter solves the issue when using it locally (by executing Spring Boot), then everything works out, no instantiation errors while still keeping the List<> interface.

Additionally I also updated the library to 1.1.1.

Now I do not have an error anymore, but the result is also not correct:

• Executing the request /test?list=1&list=2&list=3 on AWS Lambda I now get a list with only one entry: [3]
• Executing the request /test?list=1,2,3 on AWS Lambda I now get a list with only one entry: [1%2C2%2C3]

[sapessi]

Hey @Juchar, the first issue is expected. It's caused by the fact that API Gateway uses a simple Map to send query string parameters to Lambda - for this reason the parameter list only contains the last value that was read for it.

In the second case, it looks like Spring is not URLDecoding the parameter before trying to read it as a list. This is a change we made for version 1.1.1, fixes things with Jersey but looks like it may be causing an issue with Spring. I'll investigate and if needed publish a fix today.

[sapessi]

Sigh, it does indeed look like a bug. I'll work on it and publish a 1.1.3 later today. I'll resolve this tickets once it's out.

[sapessi]

Hey @Juchar, could you test with 1.2-SNAPSHOT in the core branch of this repo?

[sapessi]

@Juchar, Release 1.1.3 is making its way to maven central and it should fix this issue. Feel free to re-open this if you still run into problems. As I said API Gateway uses a simple Map to send query string parameters to Lambda - for this reason you cannot have multiple query string parameters with the same name as a list.

[Juchar]

@sapessi Did not have the time on the weekend but just tried it out and it seems that everything works. Thank you for the quick solution! Great support!