Java 和 YAML : how to parse multiple yaml documents and merge them to a single YAML representation?

Question

假设我有一个文件，defaults.yaml:

pool:
  idleConnectionTestPeriodSeconds: 30
  idleMaxAgeInMinutes: 60
  partitionCount: 4
  acquireIncrement: 5
  username: dev
  password: dev_password

和另一个文件，production.yaml:

pool:
  username: prod
  password: prod_password

在运行时，我如何读取这两个文件并将它们合并为一个文件，以便应用程序“看到”以下内容？

pool:
  idleConnectionTestPeriodSeconds: 30
  idleMaxAgeInMinutes: 60
  partitionCount: 4
  acquireIncrement: 5
  username: prod
  password: prod_password

比方说，SnakeYAML 这可能吗？还有其他工具吗？

我知道一个选择是将多个文件作为 map 读取，然后自己合并它们，将合并呈现为单个临时文件，然后读取它，但这是一个重量级的解决方案。现有工具可以做到这一点吗？

Answer 1

您可以使用 Jackson，关键是使用 ObjectMapper.readerForUpdating() 并使用 @JsonMerge 注释该字段(或者下一个对象中所有缺失的字段将覆盖旧的):

专家:

    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.9.9</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.dataformat</groupId>
        <artifactId>jackson-dataformat-yaml</artifactId>
        <version>2.9.9</version>
    </dependency>

代码:

public class TestJackson {
    public static void main(String[] args) throws IOException {
        ObjectMapper mapper = new ObjectMapper(new YAMLFactory());
        MyConfig myConfig = new MyConfig();
        ObjectReader objectReader = mapper.readerForUpdating(myConfig);
        objectReader.readValue(new File("misc/a.yaml"));
        objectReader.readValue(new File("misc/b.yaml"));
        System.out.println(myConfig);
    }

    @Data
    public static class MyConfig {
        @JsonMerge
        private Pool pool;
    }

    @Data
    public static class Pool {
        private Integer idleConnectionTestPeriodSeconds;
        private Integer idleMaxAgeInMinutes;
        private Integer partitionCount;
        private Integer acquireIncrement;
        private String username;
        private String password;
    }
}