[Java] 如何利用Jackson序列化忽略指定类型的属性详解

{
 "namespace": "cc.unmi.data",
 "type": "record",
 "name": "user",
 "fields": [
 {"name": "name", "type": "string"},
 {"name": "address", "type": ["string", "null"]}
 ]
}

objectmapper objectmapper = new objectmapper() ;
user user = user.newbuilder().setname("yanbin").setaddress("chicago").build();
system.out.println(objectmapper.writevalueasstring(user));

caused by: org.apache.avro.avroruntimeexception: not a map: {"type":"record","name":"user","namespace":"cc.unmi.data","fields":[{"name":"name","type":"string"},{"name":"address","type":["string","null"]}]}
  at org.apache.avro.schema.getvaluetype(schema.java:294)
  at com.fasterxml.jackson.databind.ser.beanpropertywriter.serializeasfield(beanpropertywriter.java:664)
  at com.fasterxml.jackson.databind.ser.std.beanserializerbase.serializefields(beanserializerbase.java:689)

public org.apache.avro.schema getschema() { return schema$; }

public schema getvaluetype() {
throw new avroruntimeexception("not a map: "+this);
}

• 凡是 org.apache.avro.schema 的属性不被序列化(schema 输出确实用处不大)
  
• 或对于org.apache.avro.schema 类型的属性定制序列化，比如输出为完整类名，或 schema 定义的文本内容
  
• 再来一个，对 specificrecordbase 类型的 schema 名称的属性进行忽略(avro 类型继承自 specificrecordbase)
  

@jsonignoretype
@interface ignoreavroschemafield {
}

objectmapper objectmapper = new objectmapper() ;
objectmapper.addmixin(schema.class, ignoreavroschemafield.class);
 
user user = user.newbuilder().setname("yanbin").setaddress("chicago").build();
system.out.println(objectmapper.writevalueasstring(user));

{"name":"yanbin","address":"chicago"}

class avroschemaserializer extends jsonserializer<schema> {
 
 @override
 public void serialize(schema value, jsongenerator jgen, serializerprovider provider) throws ioexception {
 jgen.writestring(value.getfullname()); //直接输出当前 apache avro 对象的全限类名
 }
}

objectmapper objectmapper = new objectmapper() ;
simplemodule simplemodule = new simplemodule("simplemodule", version.unknownversion());
simplemodule.addserializer(schema.class, new avroschemaserializer());
objectmapper.registermodule(simplemodule);
 
user user = user.newbuilder().setname("yanbin").setaddress("chicago").build();
system.out.println(objectmapper.writevalueasstring(user));

{"name":"yanbin","address":"chicago","schema":"cc.unmi.data.user"}

jgen.writestring(value.tostring());

system.out.println(objectmapper.writerwithdefaultprettyprinter().writevalueasstring(user));
{
 "name" : "yanbin",
 "address" : "chicago",
 "schema" : "{"type":"record","name":"user","namespace":"cc.unmi.data","fields":[{"name":"name","type":"string"},{"name":"address","type":["string","null"]}]}"
}

@jsonfilter("filter out apache avro schema field") //字符串值要与下面 addfilter("xxx") 保持一致
class propertyfiltermixin {}

objectmapper objectmapper = new objectmapper() ;
objectmapper.addmixin(specificrecordbase.class, propertyfiltermixin.class); //对 specificrecordbase 类型的对象应用
filterprovider filterprovider = new simplefilterprovider() //对 specificrecordbase 类型(如 user) 的名为 "schema" 属性屏蔽
 .addfilter("filter out apache avro schema field", simplebeanpropertyfilter.serializeallexcept("schema"));
objectmapper.setfilterprovider(filterprovider);
 
user user = user.newbuilder().setname("yanbin").setaddress("chicago").build();
system.out.println(objectmapper.writevalueasstring(user));

{"name":"yanbin","address":"chicago"}

• jackson ignore properties on marshalling
  
• how do i exclude fields with jackson not using annotations