Spring Boot 2.x列表绑定问题

Question

I'm having issues with binding some Lists after upgrading to Spring Boot 2x. The code worked in Spring 1.x and now it throws a binding error on startup. Here's my application.yml...

aws:
  geo-mappings:
    - name: USA
      regions:
        - us-west-2
        - us-west-1
        - us-east-1
        - us-east-2
    - name: California
      regions:
        - us-west-2

Here's my component class...

package com.example.demo.config.aws;


import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by goer on 4/18/17.
 */
@Component
@Scope("singleton")
@ConfigurationProperties(prefix="aws")
public class AWSConfigProvider {

    private List<GeoMappingEntry> geoMappings = new ArrayList<>();

    public List<GeoMappingEntry> getGeoMappings() {
        return this.geoMappings;
    }


}

Here's the nested object...

package com.example.demo.config.aws;

import java.util.ArrayList;
import java.util.List;


public class GeoMappingEntry {
    private String name;
    private List<String> regions = new ArrayList<>();

    public GeoMappingEntry(String name, List<String> regions) {
        this.name = name;
        this.regions = regions;
    }
}

When I try to run I get...

---

APPLICATION FAILED TO START

---

Description:

Failed to bind properties under 'aws.geo-mappings' to java.util.List:

Reason: Failed to bind properties under 'aws.geo-mappings' to java.util.List<com.example.demo.config.aws.GeoMappingEntry>

Action:

Update your application's configuration

Has anybody else run in to the same problem? Solutions? Suggestions?

Answer 1

Just incase anybody else is looking at a similar issue. It turned out that some environment variables that didn't work in previous versions of Spring are now able to actually create bindings and that's were the errors were coming from.

In this case relaxed binding from an environment var to a list such as AWS_GEOMAPPINGS_0_REGIONS_0 = us-west-2 wasn't working before but now it does. Before Spring Boot 2.0 the only way to set this from an environment var was to pass JSON via SPRING_APPLICATION_JSON , which works, but gets complicated if you are trying to deploy using some other JSON that encapsulates it (like Terraform).