Configuration File

There are two kind of file format can be used in Spring Boot
1. application.properties
2. application.yml (recommended)

Why Need Config File

To modify defaule value which be initialized by Spring Boot.

YAML vs. XML vs. properties

There are three kind of configuration file type we usually.
YAML
- ```
server:
        prot: 8081
```

XML

<server>
        <prot>8081</prot>
</server>

properties
- ```
server.prot: 8081
```

YAML Expression Syntax

Presents Number, String, Boolean value
- double quotes " "
```
input: name: "daniel \n cool"     \n 换行
```
- output: daniel 换行 cool
- single quotes ' '
```
input: name: "daniel \n cool"
```
  - output: daniel \n cool

Presents Objece, Map

friends:
        lastName: daniel
        age: 21

```
friends: {lastName: daniel,age: 21}
```

Presents List, Set

```
pets:
    - cat
    - dog
    - pig
```
```
pets: [cat,dog,pig]
```

Sample

person:
    lastName: hello
    age: 18
    boss: false
    birth: 2017/12/12
    maps: {k1: v1,k2: 12}
    lists:
            ‐ lisi
            ‐ zhaoliu
        dog:
            name: 小狗
            age: 12

Build Relationship Between YAML and Class

Sample

@Component  
// make this to container component, so that to use @ConfigurationProperties
@ConfigurationProperties(prefix="person") 
//make binding between YAML and this class, prefix is used to specify a target attribute 
public class Person {
      
  private String lastName;
  private Integer age;
  private Boolean boss;
  private Date birth;
      
  private Map<String, Object> maps;
  private List<Object> lists;
  private Dog dog; // this is a object
}