Java CommonsMultipartFile的Jackson序列化问题

我有一个具有CommonMultipartFile类型字段的bean，如下所示：

public class Placement implements Serializable {

private static final long serialVersionUID = 1L;

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

我已经将CommonsMultipartFile字段标记为transient，并尝试使用jackson库序列化为json。但出现以下错误：

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"])

---

任何帮助/建议都将不胜感激。

不清楚Jackson是如何使用的，因为原始问题中没有提供代码或说明

默认情况下，Jackson在序列化期间跳过所有临时字段

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";
}

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";
}

但是，如果瞬态字段有一个getter，那么默认情况下Jackson会在序列化过程中包含它

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";
}

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";
}

跳过getter的一个配置选项是只应用@JsonIgnore注释

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";
}

如果不可能或不希望编辑原始类定义来添加@JsonIgnore注释，则可以使用

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";
}

另一种方法是使用

@JsonIgnoreType

标记要跳过的类型

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";
}

---

如果不想序列化多部分文件，请将注释

@JsonIgnore

添加到该字段

@JsonIgnore
private CommonsMultipartFile fileData;

---

您可以阅读更多abot jackson注释。

如何公开私有字段？和getter一起？使用改进的可视性检测仪？你用什么代码来序列化？节省了我很多时间。。！！谢谢