我有很多类来自供应商,他们喜欢在属性访问时随机抛出RuntimeExceptions。
public Object getSomeProperty() {
if (!someObscureStateCheck()) {
throw new IllegalStateExcepion();
}
return calculateTheValueOfProperty(someRandomState);
}
我无法更改类,无法添加注释,为每个类定义mixins是不现实的,因为这部分堆栈会经常更改。
如果杰克逊的getter抛出异常,我如何让Jackson忽略一个属性?
答案 0 :(得分:15)
要在杰克逊中执行custom serialization,您可register a module使用BeanSerializerModifier
指定所需的任何修改。在您的情况下,BeanPropertyWriter.serializeAsField
是负责序列化单个字段的方法,因此您应该创建自己的BeanPropertyWriter
忽略字段序列化的异常,并注册一个使用BeanSerializerModifier
的模块{ {3}}用您自己的实现替换所有默认BeanPropertyWriter
实例。以下示例演示:
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.fasterxml.jackson.databind.ser.*;
import java.io.IOException;
import java.util.List;
import java.util.stream.Collectors;
public class JacksonIgnorePropertySerializationExceptions {
public static void main(String[] args) throws IOException {
ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new SimpleModule().setSerializerModifier(new BeanSerializerModifier() {
@Override
public List<BeanPropertyWriter> changeProperties(SerializationConfig config, BeanDescription beanDesc, List<BeanPropertyWriter> beanProperties) {
return beanProperties.stream().map(bpw -> new BeanPropertyWriter(bpw) {
@Override
public void serializeAsField(Object bean, JsonGenerator gen, SerializerProvider prov) throws Exception {
try {
super.serializeAsField(bean, gen, prov);
} catch (Exception e) {
System.out.println(String.format("ignoring %s for field '%s' of %s instance", e.getClass().getName(), this.getName(), bean.getClass().getName()));
}
}
}).collect(Collectors.toList());
}
}));
mapper.writeValue(System.out, new VendorClass());
}
public static class VendorClass {
public String getNormalProperty() {
return "this is a normal getter";
}
public Object getProblematicProperty() {
throw new IllegalStateException("this getter throws an exception");
}
public String getAnotherNormalProperty() {
return "this is a another normal getter";
}
}
}
上面的代码使用Jackson 2.7.1和Java 1.8输出以下内容:
ignoring java.lang.reflect.InvocationTargetException for field 'problematicProperty' of JacksonIgnorePropertySerializationExceptions$VendorClass instance
{"normalProperty":"this is a normal getter","anotherNormalProperty":"this is a another normal getter"}
显示引发getProblematicProperty
的{{1}}将从序列化值中省略。