Jackson Serialization issue with CommonsMultipartFile

I have a bean with CommonsMultipartFile type field like so:

public class Placement implements Serializable {

private static final long serialVersionUID = 1L;

private long placementId;
private String type;
private String placement;
private transient CommonsMultipartFile fileData;

I have marked CommonsMultipartFile field as transient and trying to serialize to json using jackson library. But getting following error:

org.codehaus.jackson.map.JsonMappingException: No serializer found for class java.io.ByteArrayInputStream and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: nextag.travel.dashboard.model.Placement["fileData"]->org.springframework.web.multipart.commons.CommonsMultipartFile["inputStream"])

Any help/ suggestions would be开发者_高级运维 highly appreciated.

It's not clear how Jackson is being used, as no code or description was provided in the original question.

By default, Jackson skips all transient fields during serialization.

import java.io.Serializable;

import org.codehaus.jackson.annotate.JsonAutoDetect.Visibility;
import org.codehaus.jackson.map.ObjectMapper;

public class Foo
{
  public static void main(String[] args) throws Exception
  {
    ObjectMapper mapper = new ObjectMapper();
    mapper.setVisibilityChecker(mapper.getVisibilityChecker().withFieldVisibility(Visibility.ANY));
    System.out.println(mapper.writeValueAsString(new Placement()));
    // output:  {"placementId":42,"type":"OK","placement":"left"}
    // transient fields are skipped by default
  }
}

class Placement implements Serializable
{
  private static final long serialVersionUID = 1L;

  private long placementId = 42;
  private String type = "OK";
  private String placement = "left";
  private transient CommonsMultipartFile fileData = new CommonsMultipartFile();
}

class CommonsMultipartFile
{
  private String name = "Fred";
}

If there is a getter for the transient field, however, then by default Jackson includes it during serialization.

import java.io.Serializable;

import org.codehaus.jackson.annotate.JsonAutoDetect.Visibility;
import org.codehaus.jackson.map.ObjectMapper;

public class Foo
{
  public static void main(String[] args) throws Exception
  {
    ObjectMapper mapper = new ObjectMapper();
    mapper.setVisibilityChecker(mapper.getVisibilityChecker().withFieldVisibility(Visibility.ANY));
    System.out.println(mapper.writeValueAsString(new Placement()));
    // output: {"placementId":42,"type":"OK","placement":"left","fileData":{"name":"Fred"}}
    // transient fields with getters are not skipped by default
  }
}

class Placement implements Serializable
{
  private static final long serialVersionUID = 1L;

  private long placementId = 42;
  private String type = "OK";
  private String placement = "left";
  private transient CommonsMultipartFile fileData = new CommonsMultipartFile();

  public CommonsMultipartFile getFileData() {return fileData;}
}

class CommonsMultipartFile
{
  private String name = "Fred";
}

One configuration option to skip the getter is to just apply the @JsonIgnore annotation.

import java.io.Serializable;

import org.codehaus.jackson.annotate.JsonAutoDetect.Visibility;
import org.codehaus.jackson.annotate.JsonIgnore;
import org.codehaus.jackson.map.ObjectMapper;

public class Foo
{
  public static void main(String[] args) throws Exception
  {
    ObjectMapper mapper = new ObjectMapper();
    mapper.setVisibilityChecker(mapper.getVisibilityChecker().withFieldVisibility(Visibility.ANY));
    System.out.println(mapper.writeValueAsString(new Placement()));
    // output: {"placementId":42,"type":"OK","placement":"left"}
    // getters marked with @JsonIgnore are ignored
  }
}

class Placement implements Serializable
{
  private static final long serialVersionUID = 1L;

  private long placementId = 42;
  private String type = "OK";
  private String placement = "left";
  private transient CommonsMultipartFile fileData = new CommonsMultipartFile();

  @JsonIgnore
  public CommonsMultipartFile getFileData() {return fileData;}
}

class CommonsMultipartFile
{
  private String name = "Fred";
}

If it's not possible or desirable to edit the original class definition to add the @JsonIgnore annotation, a Mix-In can be used.

import java.io.Serializable;

import org.codehaus.jackson.annotate.JsonAutoDetect.Visibility;
import org.codehaus.jackson.annotate.JsonIgnore;
import org.codehaus.jackson.map.ObjectMapper;

public class Foo
{
  public static void main(String[] args) throws Exception
  {
    ObjectMapper mapper = new ObjectMapper();
    mapper.setVisibilityChecker(mapper.getVisibilityChecker().withFieldVisibility(Visibility.ANY));
    mapper.getSerializationConfig().addMixInAnnotations(Placement.class, SkipFileDataMixIn.class);
    System.out.println(mapper.writeValueAsString(new Placement()));
    // output: {"placementId":42,"type":"OK","placement":"left"}
    // getters marked with @JsonIgnore are ignored
  }
}

abstract class SkipFileDataMixIn
{
  @JsonIgnore
  public abstract CommonsMultipartFile getFileData();
}

class Placement implements Serializable
{
  private static final long serialVersionUID = 1L;

  private long placementId = 42;
  private String type = "OK";
  private String placement = "left";
  private transient CommonsMultipartFile fileData = new CommonsMultipartFile();

  public CommonsMultipartFile getFileData() {return fileData;}
}

class CommonsMultipartFile
{
  private String name = "Fred";
}

Another approach is to mark the type to be skipped with @JsonIgnoreType.

import java.io.Serializable;

import org.codehaus.jackson.annotate.JsonAutoDetect.Visibility;
import org.codehaus.jackson.annotate.JsonIgnoreType;
import org.codehaus.jackson.map.ObjectMapper;

public class Foo
{
  public static void main(String[] args) throws Exception
  {
    ObjectMapper mapper = new ObjectMapper();
    mapper.setVisibilityChecker(mapper.getVisibilityChecker().withFieldVisibility(Visibility.ANY));
    System.out.println(mapper.writeValueAsString(new Placement()));
    // output: {"placementId":42,"type":"OK","placement":"left"}
    // Types marked with @JsonIgnoreType are ignored during serialization.
  }
}

class Placement implements Serializable
{
  private static final long serialVersionUID = 1L;

  private long placementId = 42;
  private String type = "OK";
  private String placement = "left";
  private transient CommonsMultipartFile fileData = new CommonsMultipartFile();

  public CommonsMultipartFile getFileData() {return fileData;}
}

@JsonIgnoreType
class CommonsMultipartFile
{
  private String name = "Fred";
}

If you do not want to serialize the multipartfile then add the annotation @JsonIgnore to the field.

@JsonIgnore
private CommonsMultipartFile fileData;

You can read more abot jackson annotations here.