@ConfigurationProperties:松散绑定、校验与构造器绑定

  application.properties 里写 app.first-name=v:
    firstName=v, maxConnections=0, hosts=[], labels={}
  application.properties 里写 app.firstName=v:
    firstName=v, maxConnections=0, hosts=[], labels={}
  application.properties 里写 app.first_name=v:
    firstName=v, maxConnections=0, hosts=[], labels={}
  application.properties 里写 app.firstname=v:
    firstName=v, maxConnections=0, hosts=[], labels={}
  application.properties 里写 app.FIRST-NAME=v:
    firstName=v, maxConnections=0, hosts=[], labels={}
  操作系统环境变量 APP_FIRSTNAME=v:
    firstName=v, maxConnections=0, hosts=[], labels={}
  操作系统环境变量 APP_FIRST_NAME=v:
    firstName=v, maxConnections=0, hosts=[], labels={}
  操作系统环境变量 APP_FIRST__NAME=v:
    firstName=null, maxConnections=0, hosts=[], labels={}

  app.hosts=a,b,c:
    firstName=null, maxConnections=0, hosts=[a, b, c], labels={}
  app.hosts[0]=x 与 app.hosts[1]=y:
    firstName=null, maxConnections=0, hosts=[x, y], labels={}
  app.hosts[1]=y(没有 [0]):
    启动失败:Description: Binding to target [Bindable@25d3cfc8 type = java.util.List<java.lang.String>, value = 'provided', annotations = array<Annotation>[[empty]], bindMethod = [null]] failed: Property: app.hosts[1] Value: "y" Origin: … Reason: The elements [app.hosts[1]] were left unbound. Action: Update your application's configuration
  环境变量 APP_HOSTS_0=e0、APP_HOSTS_1=e1:
    firstName=null, maxConnections=0, hosts=[e0, e1], labels={}
  环境变量 APP_HOSTS=a,b:
    firstName=null, maxConnections=0, hosts=[a, b], labels={}
  文件里 app.hosts=a,b,c,系统属性 -Dapp.hosts[0]=z(不同来源的列表合并还是替换):
    firstName=null, maxConnections=0, hosts=[z], labels={}
  app.labels.env=prod:
    firstName=null, maxConnections=0, hosts=[], labels={env=prod}
  app.labels.a.b=x(key 里有点号,不加方括号):
    firstName=null, maxConnections=0, hosts=[], labels={a.b=x}
  app.labels[a.b]=x(加方括号):
    firstName=null, maxConnections=0, hosts=[], labels={a.b=x}
  环境变量 APP_LABELS_ENV=prod:
    firstName=null, maxConnections=0, hosts=[], labels={env=prod}
  文件里 app.labels.a=1,系统属性 -Dapp.labels.b=2(不同来源的 Map 合并还是替换):
    firstName=null, maxConnections=0, hosts=[], labels={b=2, a=1}

  Duration(没有单位的数字默认毫秒)
  "30s" → PT30S
  "PT30S" → PT30S
  "2m" → PT2M
  "500" → PT0.5S
  "1.5s" → 失败:'1.5s' is not a valid duration
  "30 s" → 失败:'30 s' is not a valid duration
  "1d" → PT24H
  "-5s" → PT-5S
  "PT-5S" → PT-5S
  "30seconds" → 失败:'30seconds' is not a valid duration
  Duration(@DurationUnit(SECONDS))
  "500" → PT8M20S
  "500ms" → PT0.5S
  "2m" → PT2M
  DataSize
  "10MB" → 10485760B
  "10mb" → 失败:Unknown data unit suffix 'mb'
  "1024" → 1024B
  "1KB" → 1024B
  "1.5MB" → 失败:'1.5MB' does not match data size pattern
  "10 MB" → 10485760B
  "2GB" → 2147483648B
  boolean
  "true" → true
  "TRUE" → true
  "yes" → true
  "on" → true
  "1" → true
  "y" → 失败:Invalid boolean value 'y'
  "no" → false
  "off" → false
  "0" → false
  "t" → 失败:Invalid boolean value 't'
  "" → null
  枚举 Mode{FAST_MODE,SLOW_MODE}
  "FAST_MODE" → FAST_MODE
  "fast-mode" → FAST_MODE
  "fast_mode" → FAST_MODE
  "fastMode" → FAST_MODE
  "FAST-MODE" → FAST_MODE
  "fast mode" → FAST_MODE
  "fastmode" → FAST_MODE
  "Fast_Mode" → FAST_MODE
  int
  "42" → 42
  "042" → 42
  "0x1F" → 31
  "1,000" → 失败:For input string: "1,000"
  "3.0" → 失败:For input string: "3.0"
  "1000L" → 失败:For input string: "1000L"
  "" → null
  List<String>(逗号分隔)
  "a,b,c" → [a, b, c]
  "a, b ,c" → [a, b, c]
  "a,,c" → [a, , c]
  "a" → [a]
  "" → []
  "a;b" → [a;b]
  -- 绑定失败时的启动报错
  app.max-connections=abc:
    启动失败:Description: Failed to bind properties under 'app.max-connections' to int: Property: app.max-connections Value: "abc" Origin: … Reason: failed to convert java.lang.String to int (caused by java.lang.NumberFormatException: For input string: "abc") Action: Update your application's configuration

  name 空白、pool=11,inner.url 与 inner2.url 都填了:
    启动失败:Description: Binding to target demo.V failed: Property: v.name Value: "" Origin: … Reason: must not be blank Property: v.pool Value: "11" Origin: … Reason: must be less than or equal to 10 Action: Update your application's configuration
  name 与 pool 正常,inner.url(嵌套对象,没有 @Valid)缺失,inner2.url 填了:
    V{name=ok, pool=5, inner.url=null, inner2.url=u2}
  name 与 pool 正常,inner2.url(嵌套对象,有 @Valid)缺失,inner.url 填了:
    启动失败:Description: Binding to target demo.V failed: Property: v.inner2.url Value: "null" Reason: must not be blank Action: Update your application's configuration
  类上没有 @Validated,字段上写了 @NotBlank,name 缺失:
    NoVal{name=null}(类上没有 @Validated)
  类上有 @Validated,但运行时 classpath 里没有 hibernate-validator(只有 spring-boot-starter),name 空白、pool=11:
    V{name=, pool=11, inner.url=null, inner2.url=null}

  字段是 final、只有 getter 没有 setter,配置 g.name=changed:
    启动失败:Description: Failed to bind properties under 'g' to demo.Getters: Property: g.name Value: "changed" Origin: … Reason: java.lang.IllegalStateException: No setter found for property: name Action: Update your application's configuration
  字段不是 final、只有 getter 没有 setter,配置 g.count=7:
    启动失败:Description: Failed to bind properties under 'g' to demo.Getters: Property: g.count Value: "7" Origin: … Reason: java.lang.IllegalStateException: No setter found for property: count Action: Update your application's configuration
  同样的类,g.name、g.count 都不配:
    Getters{name=init, count=1}(两个字段都只有 getter,没有 setter)
  record,什么都不配:
    Rec[name=null, count=0, tags=null, m=null, in=null, inDef=Inner[url=null, port=8080], withDef=dflt]
  record,配置 rec.name=n、rec.count=3、rec.tags=x,y、rec.m.k=v、rec.in.url=u、rec.in-def.url=u2、rec.with-def=given:
    Rec[name=n, count=3, tags=[x, y], m={k=v}, in=Inner[url=u, port=8080], inDef=Inner[url=u2, port=8080], withDef=given]
  类有两个构造器、都没有 @ConstructorBinding,配置 multi.a=1:
    启动失败(没有 FailureAnalyzer 报告,堆栈里的异常):Caused by: java.lang.NoSuchMethodException: demo.Multi.<init>()
  类有两个构造器、其中一个标了 @ConstructorBinding,配置 multi2.a=1、multi2.b=2:
    Multi2{a=1, b=2}
  类只有一个带参构造器(没有注解)又有 setter,配置 both.a=1、both.b=2:
    Both{a=1, b=field-default}

  app.first-name=initial 启动,启动之后再往 Environment 里加新值:
    firstName=initial, maxConnections=0, hosts=[], labels={}
    启动之后在 Environment 最前面加 app.first-name=changed:
      Environment.getProperty        = changed
      @ConfigurationProperties bean  = initial
      @Value 字段                    = initial
      Binder.get(env).bind(...) 重新绑定 = changed