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1.1.1. 前言

近期在使用ObjectMapper对象将json转化为对象的时候，出错，解决这个异常之后，打算分享一下，免得别人也遇到类似的问题，具体的出错信息部分如下所示：

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field

1.1.2. jar包

我的maven pom.xml如下所示：

<jackson-2-version>2.4.2</jackson-2-version>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<exclusions>
<exclusion>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
</exclusion>
</exclusions>
<version>${jackson-2-version}</version>
</dependency>

下面还原一下问题的场景。

1.1.3. bean实体

需要将json转化的实体对象User类如下：

public class User {
private long id;
private String name;
private boolean flag;
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public boolean isFlag() {
return flag;
}
public void setFlag(boolean flag) {
this.flag = flag;
}
@Override
public String toString() {
return "User [id=" + id + ", name=" + name + ", flag=" + flag + "]";
}
}

1.1.4. 测试

具体的测试程序如下所示：

String s = "{\"id\":1,\"name\":\"test\",\"age\":19}";

ObjectMapper mapper = new ObjectMapper();

User value = mapper.readValue(s, User.class);

System.out.println(value);

因为user类中的属性有id、name、flag，而对应的s字符串中有age字段所以不匹配，报错信息如下：

Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "age" (class com.daling.bpmn.test.User), not marked as ignorable (3 known properties: "id", "name", "flag"])

at [Source: {"id":1,"name":"test","age":19}; line: 1, column: 31] (through reference chain: com.daling.bpmn.test.User["age"])

at com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:51)

at com.fasterxml.jackson.databind.DeserializationContext.reportUnknownProperty(DeserializationContext.java:731)

at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:915)

at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty(BeanDeserializerBase.java:1298)

at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownVanilla(BeanDeserializerBase.java:1276)

at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:243)

at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:118)

at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3051)

at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2146)

at com.daling.vrm.controller.product.NewShelvesController.main(NewShelvesController.java:71)

1.1.5. 最终解决方案

1.1.5.1. 第一种解决方案

ObjectMapper 对象添加

mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

String s = "{\"id\":1,\"name\":\"test\",\"age\":19}";

ObjectMapper mapper = new ObjectMapper();

mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

User value = mapper.readValue(s, User.class);

System.out.println(value);

1.1.5.2. 第二种解决方案

在需要转化的对象的类中添加注解，注解信息如下：

@JsonIgnoreProperties(ignoreUnknown = true)

public class User

...

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