YAML的设计者认为在配置文件中所要表达的数据内容有三种类型：标量(Scalar，如字符串和整数等)、序列（Sequence，如数组）和Mapping（类似hash的key/value pair）。

一、读取键值对

\\customer.yaml
firstName: "John"
lastName: "Doe"
age: 20

Yaml yaml = new Yaml();
Object result= yaml.load(new FileReader("D:\\config\\customer.yaml"));

result加载为LinkedHashMap类。

二、写入键值对

    Map<String,Object> object = new LinkedHashMap<>();
    object.put("firstName","John");
    object.put("lastName","Doe");
    object.put("age",20);
    Yaml yaml = new Yaml();
    yaml.dump(object,new FileWriter("D:\\config\\object.yaml"));
    return object.toString();

\\object.yaml
{firstName: John, lastName: Doe, age: 20}

三、写入java对象

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Pojo {
    public int id;
    public String name;
}

Yaml yaml = new Yaml();
List<Pojo> arr = new ArrayList<>();
Pojo p1 = new Pojo(1,"hello");
Pojo p2 = new Pojo(2,"world");
arr.add(p1);
arr.add(p2);
yaml.dump(arr,new FileWriter("D:\\config\\pojo.yaml"));

\\pojo.yaml
- !!com.example.yamldemo.domain.Pojo {id: 1, name: hello}
- !!com.example.yamldemo.domain.Pojo {id: 2, name: world}

四、读取复杂键值对

\\application
spring:
  profiles:
    active: instance1
  application:
    name: eureka-service
eureka:
  client:
    #由于该应用为注册中心,设置为false,表明不向注册中心注册自己
    register-with-eureka: false
  server:
    enable-self-preservation: false
    #是否从eureka服务器获取注册信息，这里不需要
    fetch-registry: false
logging:
  level:
    com:
      netflix:
        eureka: OFF
        discovery: OFF
management:
  endpoints:
    web:
      exposure:
        include: '*'
  endpoint:
      health:
        show-details: ALWAYS
---
spring:
  profiles: instance1
server:
  port: 8761
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8762/eureka/
---
spring:
  profiles: instance2
server:
  port: 8762
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/

Yaml yaml = new Yaml();
Iterable<Object> result = yaml.loadAll(new FileReader("D:\\config\\application.yaml"));
log.info(result.getClass());
for(Object object:result){
    log.info(object.getClass());
    for(Map.Entry entry:((LinkedHashMap<Object,Object>)object).entrySet()){
        log.info(entry.getKey());
        log.info(entry.getKey().getClass());
        log.info(entry.getValue());
        log.info(entry.getValue().getClass());
    }
}

由输出可得它们都是>类型

五、读取java对象

\\address.yaml
lines: |
  458 Walkman Dr.
  Suite #292
city: Royal Oak
state: MI
postal: 48046

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Address {
    private String lines;
    private String city;
    private String state;
    private Integer postal;
}

Yaml yaml = new Yaml();
Address ret = yaml.loadAs(new FileReader("D:\\config\\address.yaml"), Address.class);
log.info(ret.getCity());
return ret.toString();

注意

把yaml文件放入项目的时候犯了大错，文件夹定义成了config，里面又有application.yaml，所以配置文件加载错了
。
因此我去了解下yaml、properties文件加载的优先级，最高优先级是项目目录下的config文件夹里面的application，第二就是项目目录下的application，第三就是resource下的config文件夹里的application，第四就是resource的application，还有一个规则就是application.properties加载优先级比application.yaml优先级高。