京公网安备11010502063487号字符串怎么变成 int、枚举、List、日期?自己的类型怎么注册转换器?绑定表单时写错了会怎样?旧的 PropertyEditor 还有用吗?这篇在 Spring Framework 7.0.9 上逐项验证。
"42" → Integer Integer:42 "true" → Boolean Boolean:true "yes" → Boolean Boolean:true "RED" → Color Color:RED "red" → Color ✗ ConversionFailedException: Failed to convert from type [java.lang.String] to type [demo.Main$Color] for value [red] "1,2,3" → int[] int[][1, 2, 3] "1,2,3" → List<Integer> ArrayList:[1, 2, 3] "PT1M30S" → Duration ✗ ConverterNotFoundException: No converter found capable of converting from type [java.lang.String] to type [java.time.Duration] "30s" → Duration ✗ ConverterNotFoundException: No converter found capable of converting from type [java.lang.String] to type [java.time.Duration] "2026-10-19" → LocalDate ✗ ConverterNotFoundException: No converter found capable of converting from type [java.lang.String] to type [java.time.LocalDate] "3.14" → BigDecimal BigDecimal:3.14 "a" → Character Character:a "zh-CN" → Locale Locale:zh_CN "1,2" → Point ✗ ConverterNotFoundException: No converter found capable of converting from type [java.lang.String] to type [demo.Main$Point]
基本类型、枚举、数组与集合开箱即用;Duration、LocalDate 要用带格式化的 ConversionService。
注册 Converter<String, Point> 后 convert("3, 4", Point) → Point[x=3, y=4];canConvert(String→Point) = true;canConvert(Point→String) = false
Point → String(没有反向转换器):ConverterNotFoundException: No converter found capable of converting from type [demo.Main$Point] to type [java.lang.String]
注册 Formatter<Point> 后:"(5;6)" → Point[x=5, y=6];Point(5,6) → String:(5;6)(一个 Formatter 同时注册了两个方向)
没有注册任何转换器的 DefaultConversionService:ConverterNotFoundException: No converter found capable of converting from type [java.lang.String] to type [demo.Main$Point]Converter 单向,Formatter 同时负责 parse 和 print。
绑定成功的字段:day=2026-10-19 price=9.90 count=7 color=GREEN pt=Point[x=10, y=20] nums=[4, 5, 6] timeout=PT5S formatted(@DateTimeFormat yyyy/MM/dd)=2026-10-19 money(@NumberFormat #,##0.00)=1234.50;错误数 0
全部写错的输入:错误数 5
字段 day:code=typeMismatch 被拒绝的值=19/10/2026
字段 count:code=typeMismatch 被拒绝的值=seven
字段 color:code=typeMismatch 被拒绝的值=BLUE
字段 pt:code=typeMismatch 被拒绝的值=1;2
字段 price:code=typeMismatch 被拒绝的值=9.9.9
出错的字段没有被赋值:g.day=null g.count=0 g.color=null(保持默认值)DataBinder 把转换失败变成 FieldError,出错的字段保持默认值。
只有 ConversionService:pt = Point[x=3, y=4] 同时有 ConversionService 和给 Point 注册的 PropertyEditor(它总是产生 Point(-1,-1)):pt = Point[x=-1, y=-1](谁优先)
给绑定器注册的 PropertyEditor 会盖过 ConversionService。