使用jackson 序列化java對象的時候報異常:

com.fasterxml.jackson.databind.JsonMappingException:?(was?java.lang.NullPointerException)?(through?reference?chain:?com.chanjet.gov.Student["age"])at?com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:218)at?com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:183)at?com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:155)at?com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:512)at?com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:117)at

被序列化的類:

package?com.chanjet.gov;import?org.springframework.web.bind.annotation.ModelAttribute;import?com.fasterxml.jackson.annotation.JsonAutoDetect; import?com.fasterxml.jackson.annotation.JsonIgnoreProperties; import?com.fasterxml.jackson.annotation.JsonInclude;/***?Created?by?JasonQin?on?2015/7/1.*/ @JsonAutoDetect @JsonIgnoreProperties(ignoreUnknown?=?true) @JsonInclude(JsonInclude.Include.NON_NULL) public?class?Student??{public?Student()?{}/****?用戶數顯示名稱*/public?String?name;/****?每用戶的免費存儲空間*/public?Integer?age;public?String?getName()?{return?name;}public?int?getAge()?{return?age;} }

測試方法:

@Testpublic?void?test_PolicyInfo(){ObjectMapper?mapper?=?new?ObjectMapper();Student?s=new?Student();try?{System.out.println(mapper.writeValueAsString(s));}?catch?(JsonGenerationException?e)?{e.printStackTrace();}?catch?(JsonMappingException?e)?{e.printStackTrace();}?catch?(IOException?e)?{e.printStackTrace();}}

?原因:Student 類中成員變量age的屬性是Integer(包裝類型),但是在對應的getter方法中,返回的卻是基本類型int.

解決方法:

方式一:修改getter方法,返回值改為包裝類型Integer

方式二:

修改getter方法為:

public?int?getAge()?{if(age==null){return?0;}return?age;}

參考:http://www.cnblogs.com/jimmy-c/p/3978799.html

http://hw1287789687.iteye.com/blog/2255940

轉載于:https://blog.51cto.com/huangkunlun520/1711398

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