Master Spring Boot YAML: Configure Complex Objects with Ease

Environment: Spring Boot 2.7.12

1. Introduction

In Spring Boot, configuration files (.yml, .yaml, or .properties) define various application parameters. When using YAML, you can structure complex objects and settings in a readable way. This article explores how to configure complex objects using .yml files.

2. Required Dependency

<dependencies>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
  </dependency>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-configuration-processor</artifactId>
    <optional>true</optional>
  </dependency>
</dependencies>

The spring-boot-configuration-processor dependency enables IDE assistance for custom configuration properties in YAML.

3. Configuration Methods

3.1 Simple Property Configuration

@Component
@ConfigurationProperties(prefix = "pack")
public class ConfigProperties {
  private String name;
  private Integer count;
  private Boolean enable;
}

Corresponding YAML:

pack:
  count: 1
  enable: true
  name: 测试

3.2 List and Map Collections

List

Method 1:

private List<String> categorys = new ArrayList<>();
pack:
  categorys:
  - 足球
  - 篮球

Method 2:

pack:
  categorys: 足球, 篮球

Method 3:

pack:
  categorys: [足球, 篮球]

Map

Method 1:

private Map<String, String> params = new HashMap<>();
pack:
  params:
    p1: v1
    p2: v2
    p3: v3

Method 2:

pack:
  params: {p1: v1, p2: v2, p3: v3}

3.3 Nested Objects

public class Person {
  private String name;
  private Integer age;
}
private Person person;

YAML:

pack:
  person:
    age: 10
    name: 张三

3.4 Collections of Objects

List of Objects

Method 1:

private List<Person> persons = new ArrayList<>();
pack:
  persons:
  - age: 20
    name: 田七
  - age: 30
    name: 王五

Method 2:

pack:
  persons:
  - {name: 田七, age: 20}
  - {name: 王五, age: 30}

Map of Objects

Method 1:

private Map<String, Person> mappings = new HashMap<>();
pack:
  mappings:
    m1:
      age: 40
      name: 甜甜
    m2:
      age: 50
      name: 莉莉

Method 2:

pack:
  mappings:
    m1: {name: 田七, age: 20}
    m2: {name: 王五, age: 30}

Method 3:

pack:
  mappings: {m1: {name: 田七, age: 20}, m2: {name: 王五, age: 30}}

3.5 Complete Example

@Component
@ConfigurationProperties(prefix = "pack")
public class ConfigProperties {
  private String name;
  private Integer count;
  private Boolean enable;
  private List<String> categorys = new ArrayList<>();
  private List<Person> persons = new ArrayList<>();
  private Map<String, String> params = new HashMap<>();
  private Map<String, Person> mappings = new HashMap<>();
  private Person person;
}

YAML:

pack:
  count: 1
  enable: true
  name: 测试
  categorys: [足球, 篮球]
  params: {p1: v1, p2: v2, p3: v3}
  person:
    age: 10
    name: 张三
  persons:
  - {name: 田七, age: 20}
  - {name: 王五, age: 30}
  mappings: {m1: {name: 田七, age: 20}, m2: {name: 王五, age: 30}}

Result screenshot:

Additional illustration:

End of tutorial.