現在我們的application.properties檔案內容是：

server.port=8090
server.session-timeout=30
server.context-path=
server.tomcat.max-threads=0
server.tomcat.uri-encoding=UTF-8

spring.datasource.url = jdbc:mysql://localhost:3306/newbirds
spring.datasource.username = root
spring.datasource.password = mymysql
spring.datasource.driverClassName = com.mysql.jdbc.Driver
# Specify the DBMS
spring.jpa.database = MYSQL
# Show or not log for each sql query
spring.jpa.show-sql = true
# Hibernate ddl auto (create, create-drop, update)
spring.jpa.hibernate.ddl-auto = update
# Naming strategy
spring.jpa.hibernate.naming-strategy = org.hibernate.cfg.ImprovedNamingStrategy

# stripped before adding them to the entity manager)
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect
 

yml檔案的好處，天然的樹狀結構，一目瞭然。不過當時把application.properties 改成 application.yml還是痛苦了一會兒。

下面是置換後的application.yml內容：

server:
  port: 8090
  session-timeout: 30
  tomcat.max-threads: 0
  tomcat.uri-encoding: UTF-8

spring:
  datasource:
    url : jdbc:mysql://localhost:3306/newbirds
    username : root
    password : mymysql
    driverClassName : com.mysql.jdbc.Driver
  jpa:
    database : MYSQL
    show-sql : true
    hibernate:
      ddl-auto : update
      naming-strategy : org.hibernate.cfg.ImprovedNamingStrategy
    properties:
      hibernate:
        dialect : org.hibernate.dialect.MySQL5Dialect
 

1，原有的key，例如spring.jpa.properties.hibernate.dialect，按“.”分割，都變成樹狀的配置

2，key後面的冒號，後面一定要跟一個空格

3，把原有的application.properties刪掉。然後一定要執行一下  maven -X clean install