jackson 的UnrecognizedPropertyException错误

jackson 的UnrecognizedPropertyException错误
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前段时间，使用jackson封装了json字符串转换为javabean的方法，代码如下：

Java代码
public static <T> T renderJson2Object(String json, Class clazz){
       if(!StringUtil.checkObj(json)){
            return null;
        }
        try {
            mapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS, false);
            DateFormat myDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            mapper.getSerializationConfig().setDateFormat(myDateFormat);
            return (T)mapper.readValue(json, clazz);
        } catch (IOException e) {
            log.error(e);
            throw new IllegalArgumentException(e);
        }
    }
public static <T> T renderJson2Object(String json, Class clazz){ if(!StringUtil.checkObj(json)){ return null; } try { mapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS, false); DateFormat myDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); mapper.getSerializationConfig().setDateFormat(myDateFormat); return (T)mapper.readValue(json, clazz); } catch (IOException e) { log.error(e); throw new IllegalArgumentException(e); } }

，这个方法可以根据json字符串，转换为clazz指定的类型的对象，如：

Java代码
renderJson2Object("{"name":"china","age":"<span style="white-space: normal;">5000</span>"}",Student.class);
renderJson2Object("{"name":"china","age":"5000"}",Student.class);

Student类里有name，age的get，set方法，代码如下：

Java代码
public class Student implements Serializable{
    private static final long serialVersionUID = 685922460589405829L;

    private String name;
    private String age;

   /*get set略*/
}
public class Student implements Serializable{ private static final long serialVersionUID = 685922460589405829L;
private String name; private String age;

/get set略/
}

根据上面的json字符串可以正常转换为Student对象，

但是通常情况下，从前端传json字符串到后端，json字符串的值是不可控的或者被框架修改了json字符串，如在里面添加了其他的键值对，

如现在的json字符串为："{"address":"hunan","name":"china","age":"5000"}"，

Student类里根本没有address属性，这样的情况下使用renderJson2Object方法时，会抛

Java代码
java.lang.IllegalArgumentException: org.codehaus.jackson.map.exc.UnrecognizedPropertyException: Unrecognized field "address" (Class util.Student), not marked as ignorable
java.lang.IllegalArgumentException: org.codehaus.jackson.map.exc.UnrecognizedPropertyException: Unrecognized field "address" (Class util.Student), not marked as ignorable

  意思是说Student类里没有address这个属性，所以无法正常转化，同时还指明了not marked as ignorable，即没有标明可忽略的特性，先看源码这句话的理解这句话的意思

类：org.codehaus.jackson.map.deser.BeanDeserializer中的

Java代码
@Override
    protected void handleUnknownProperty(JsonParser jp, DeserializationContext ctxt, Object beanOrClass, String propName)
        throws IOException, JsonProcessingException
    {
        ... ... ...
        <span style="color: #ff0000;">// If registered as ignorable, skip</span>
        <span style="color: #ff0000;">if (_ignoreAllUnknown ||
            (_ignorableProps != null && _ignorableProps.contains(propName))) {
            jp.skipChildren();
            return;
        }</span>
         ... ... ...
    }
@Override protected void handleUnknownProperty(JsonParser jp, DeserializationContext ctxt, Object beanOrClass, String propName) throws IOException, JsonProcessingException { ... ... ... // If registered as ignorable, skip if (_ignoreAllUnknown || (_ignorableProps != null && _ignorableProps.contains(propName))) { jp.skipChildren(); return; } ... ... ... }

   源码注释说，如果注册了忽略特性，则会跳过此步骤，那到底需要怎么忽略呢？

请再看类：org.codehaus.jackson.map.deser.BeanDeserializerFactory中的

Java代码
protected void addBeanProps(DeserializationConfig config,
            BasicBeanDescription beanDesc, BeanDeserializerBuilder builder)
        throws JsonMappingException
    {
        ... .... ...
        // Things specified as "ok to ignore"? [JACKSON-77]
        AnnotationIntrospector intr = config.getAnnotationIntrospector();
        boolean ignoreAny = false;
        {
            Boolean B = intr.findIgnoreUnknownProperties(beanDesc.getClassInfo());
            if (B != null) {
                ignoreAny = B.booleanValue();
                builder.setIgnoreUnknownProperties(ignoreAny);
            }
        }
     ... ... ...
}
protected void addBeanProps(DeserializationConfig config, BasicBeanDescription beanDesc, BeanDeserializerBuilder builder) throws JsonMappingException { ... .... ... // Things specified as "ok to ignore"? [JACKSON-77] AnnotationIntrospector intr = config.getAnnotationIntrospector(); boolean ignoreAny = false; { Boolean B = intr.findIgnoreUnknownProperties(beanDesc.getClassInfo()); if (B != null) { ignoreAny = B.booleanValue(); builder.setIgnoreUnknownProperties(ignoreAny); } } ... ... ... }

intr.findIgnoreUnknownProperties(beanDesc.getClassInfo());

会查找目标对象中，是否使用了JsonIgnoreProperties 注解，其中把注解的value值赋给了builder.setIgnoreUnknownProperties(ignoreAny);

到此Student类的正确做法为：

Java代码
<span style="color: #ff0000;">@JsonIgnoreProperties(ignoreUnknown = true) </span>
public class Student implements Serializable{
    private static final long serialVersionUID = 685922460589405829L;

    private String name;
    private String age;

   /*get set.....*/
｝
@JsonIgnoreProperties(ignoreUnknown = true) public class Student implements Serializable{ private static final long serialVersionUID = 685922460589405829L;
private String name; private String age;

/get set...../
｝

看红色注解，现在暂时找到在类中添加注解（感觉具体的pojo对象和jackson耦合），不知道有没有其他方法，设全局变量来控制，如果有朋友知道，请告诉我谢谢。。。

谢谢 up2pu 兄弟的帮助，使用mapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false)，

则无需在目标类中添加JsonIgnoreProperties注解
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原文地址：https://www.cnblogs.com/jpfss/p/10938547.html

jackson 的UnrecognizedPropertyException错误

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