swagger错误 Illegal DefaultValue null for parameter type integer

1. 环境

win10
swagger 1.9.2 具体如下

		<dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>2.9.2</version>
        </dependency>

        <!-- swagger2-UI-->
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>2.9.2</version>
        </dependency>

2. 错误

 WARN 19699 --- [nio-1111-exec-4] i.s.m.p.AbstractSerializableParameter    : Illegal DefaultValue null for parameter type integer

java.lang.NumberFormatException: For input string: ""
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) ~[na:1.8.0_171]
	at java.lang.Long.parseLong(Long.java:601) ~[na:1.8.0_171]
	at java.lang.Long.valueOf(Long.java:803) ~[na:1.8.0_171]
	at io.swagger.models.parameters.AbstractSerializableParameter.getExample(AbstractSerializableParameter.java:412) ~[swagger-models-1.5.20.jar:1.5.20]
	at sun.reflect.GeneratedMethodAccessor109.invoke(Unknown Source) ~[na:na]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_171]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_171]
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:687) [jackson-databind-2.9.6.jar:2.9.6]

3. 解决

3.1 pom中排除 swagger中原有依赖，添加新的

<!--swagger依赖-->
 
<dependency> 
    <groupId>io.springfox</groupId> 
    <artifactId>springfox-swagger2</artifactId> 
    <version>2.9.2</version> 
  <exclusions> 
      <exclusion> 
        <groupId>io.swagger</groupId> 
        <artifactId>swagger-annotations</artifactId> 
      </exclusion> 
      <exclusion> 
        <groupId>io.swagger</groupId> 
        <artifactId>swagger-models</artifactId>
      </exclusion>
  </exclusions>
</dependency>
 
<!--解决进入swagger页面报类型转换错误，排除2.9.2中的引用，手动增加1.5.21版本-->

<dependency>
  <groupId>io.swagger</groupId>
  <artifactId>swagger-annotations</artifactId>
  <version>1.5.21</version>
</dependency>
<dependency>
  <groupId>io.swagger</groupId>
  <artifactId>swagger-models</artifactId>
  <version>1.5.21</version>
</dependency>

3.2 谁先声明谁优先，把1.5.21放在上面，即可排除springfox-swagger2依赖的1.5.20版本

        <dependency>
            <groupId>io.swagger</groupId>
            <artifactId>swagger-annotations</artifactId>
            <version>1.5.21</version>
        </dependency>
        <dependency>
            <groupId>io.swagger</groupId>
            <artifactId>swagger-models</artifactId>
            <version>1.5.21</version>
        </dependency>

        <!-- swagger2-->
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>2.9.2</version>
        </dependency>

        <!-- swagger2-UI-->
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>2.9.2</version>
        </dependency>

3.3 实体类中，Integer类型的属性加@ApiModelProperty时，必须要给example参数赋值，且值必须为数字类型。

@ApiModelProperty(value = "试卷ID",example = "1")
private int pageId;

4. 解释

这是由于实体类使用@ApiModelProperty时，example属性没有赋值导致的，在AbstractSerializableParameter的getExample方法中会将数值属性的example的转换数值类返回，example的默认值是""，因此当example没有赋值时，会出现上面的异常。getExample方法如下

    @JsonProperty("x-example")
    public Object getExample() {
        if (example == null) {
            return null;
        }
        try {
            if (BaseIntegerProperty.TYPE.equals(type)) {
                return Long.valueOf(example);
            } else if (DecimalProperty.TYPE.equals(type)) {
                return Double.valueOf(example);
            } else if (BooleanProperty.TYPE.equals(type)) {
                if ("true".equalsIgnoreCase(example) || "false".equalsIgnoreCase(defaultValue)) {
                    return Boolean.valueOf(example);
                }
            }
        } catch (NumberFormatException e) {
            LOGGER.warn(String.format("Illegal DefaultValue %s for parameter type %s", defaultValue, type), e);
        }
        return example;
    }