java整合swagger報錯java.lang.NumberFormatException: For input string: ""

如果你在程序運行中經常發現像下面這樣的報錯。

java.lang.NumberFormatException: For input string: ""
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) ~[na:1.8.0_111]
    at java.lang.Long.parseLong(Long.java:601) ~[na:1.8.0_111]
    at java.lang.Long.valueOf(Long.java:803) ~[na:1.8.0_111]
    at io.swagger.models.parameters.AbstractSerializableParameter.getExample(AbstractSerializableParameter.java:412) ~[swagger-models-1.5.20.jar:1.5.20]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_111]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_111]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_111]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_111]
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:536) [jackson-databind-2.5.4.jar:2.5.4]
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:666) [jackson-databind-2.5.4.jar:2.5.4]
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:156) [jackson-databind-2.5.4.jar:2.5.4]
    at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContents(IndexedListSerializer.java:113) [jackson-databind-2.5.4.jar:2.5.4]

那麼你需要檢查使用了 @ApiModelProperty 註解且字段類型爲數字類型的屬性上，@ApiModelProperty 註解是否設置了 example 值，如果沒有，那就需要設置一下，像下面這樣。

@NotNull(message = "用戶 ID 不能爲空")
@ApiModelProperty(value = "用戶ID", required = true, example = "1000")
private Integer id;