Using Jackson Mixins and Modules to fix serialization problems

Jackson Mixins and Modules

Using Jackson Mixins and Modules to fix serialization problems

CreateUser.java

  private User createUser() {
    User user = new User();
    user.setName("me");
    Thing thing = new Thing();
    thing.setName("that");
    thing.setUser(user);
    user.setThings(Lists.newArrayList(thing));
    return user;
  }

CreateWidget.java

  private Widget createWidget() {
    Widget widget = new Widget();
    widget.setId(1);
    WidgetName name = new WidgetName();
    name.value("my widget");
    widget.setName(name);
    return widget;
  }

ModuleFailureTest.java

package com.theotherian.jackson;

import java.io.StringWriter;

import org.junit.Test;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.theotherian.jackson.dto.Widget;
import com.theotherian.jackson.dto.WidgetName;

public class ModuleTest {
  
  @Test
  public void failureWithoutProperty() throws Exception {
    Widget widget = createWidget();
    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
    StringWriter writer = new StringWriter();
    mapper.writeValue(writer, widget);
    System.out.println(writer.toString());
  }

}

ModuleSuccessTest.java

package com.theotherian.jackson;

import java.io.StringWriter;

import org.junit.Test;

import com.fasterxml.jackson.databind.Module;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.theotherian.jackson.dto.Widget;
import com.theotherian.jackson.dto.WidgetName;
import com.theotherian.jackson.serializer.WidgetNameSerializer;

public class ModuleSuccessTest {

  @Test
  public void success() throws Exception {
    Widget widget = createWidget();
    ObjectMapper mapper = new ObjectMapper();
    Module serializerModule = new SimpleModule().addSerializer(WidgetName.class, new WidgetNameSerializer());
    mapper.registerModule(serializerModule);
    StringWriter writer = new StringWriter();
    mapper.writeValue(writer, widget);
    System.out.println(writer.toString());
  }

}

ModuleTest.java

package com.theotherian.jackson;

import java.io.StringWriter;

import org.junit.Test;

import com.fasterxml.jackson.databind.Module;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.theotherian.jackson.dto.Widget;
import com.theotherian.jackson.dto.WidgetName;
import com.theotherian.jackson.serializer.WidgetNameSerializer;

public class ModuleTest {
  
  @Test
  public void failureWithException() throws Exception {
    Widget widget = createWidget();
    ObjectMapper mapper = new ObjectMapper();
    StringWriter writer = new StringWriter();
    mapper.writeValue(writer, widget);
    System.out.println(writer.toString());
  }
  
  @Test
  public void failureWithoutProperty() throws Exception {
    Widget widget = createWidget();
    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
    StringWriter writer = new StringWriter();
    mapper.writeValue(writer, widget);
    System.out.println(writer.toString());
  }
  
  @Test
  public void success() throws Exception {
    Widget widget = createWidget();
    ObjectMapper mapper = new ObjectMapper();
    Module serializerModule = new SimpleModule().addSerializer(WidgetName.class, new WidgetNameSerializer());
    mapper.registerModule(serializerModule);
    StringWriter writer = new StringWriter();
    mapper.writeValue(writer, widget);
    System.out.println(writer.toString());
  }

  private Widget createWidget() {
    Widget widget = new Widget();
    widget.setId(1);
    WidgetName name = new WidgetName();
    name.value("my widget");
    widget.setName(name);
    return widget;
  }

}

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.theotherian.jackson</groupId>
  <artifactId>jackson-mixins-and-modules</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>jackson-mixins-and-modules</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <build>
    <plugins>
      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
          <source>1.7</source>
          <target>1.7</target>
        </configuration>
      </plugin>
    </plugins>
  </build>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit-dep</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-core</artifactId>
      <version>2.3.1</version>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-annotations</artifactId>
      <version>2.3.1</version>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.3.1</version>
    </dependency>
    <dependency>
      <groupId>com.google.guava</groupId>
      <artifactId>guava</artifactId>
      <version>16.0</version>
    </dependency>
  </dependencies>
</project>

serialization-stacktrace

com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion (StackOverflowError) (through reference chain: com.theotherian.jackson.dto.User["things"]->java.util.ArrayList[0]->com.theotherian.jackson.dto.Thing["user"]->...
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:646)
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152)
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:541)
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:632)
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152)
	...
Caused by: java.lang.StackOverflowError
	...

SerializationFailureTest.java

import java.io.StringWriter;

import org.junit.Test;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.theotherian.jackson.dto.User;

public class SerializationFailureTest {
  
  @Test
  public void failure() throws Exception {
    User user = createUser();
    ObjectMapper mapper = new ObjectMapper();
    
    StringWriter writer = new StringWriter();
    mapper.writeValue(writer, user);
  }
  
}

SerializationSuccessTest.java

package com.theotherian.jackson;

import java.io.StringWriter;

import org.junit.Test;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ser.FilterProvider;
import com.fasterxml.jackson.databind.ser.impl.SimpleBeanPropertyFilter;
import com.fasterxml.jackson.databind.ser.impl.SimpleFilterProvider;
import com.google.common.collect.Lists;
import com.theotherian.jackson.dto.Thing;
import com.theotherian.jackson.dto.User;
import com.theotherian.jackson.mixin.ThingMixin;

public class SerializationSuccessTest {
  
  @Test
  public void success() throws Exception {
    User user = createUser();
    ObjectMapper mapper = new ObjectMapper();
    mapper.addMixInAnnotations(Thing.class, ThingMixin.class);
    FilterProvider filterProvider = new SimpleFilterProvider()
      .addFilter("thing filter", SimpleBeanPropertyFilter.serializeAllExcept("user"));
    mapper.setFilters(filterProvider);
    
    StringWriter writer = new StringWriter();
    mapper.writeValue(writer, user);
  }

}

SerializationTest.java

package com.theotherian.jackson;

import java.io.StringWriter;

import org.junit.Test;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ser.FilterProvider;
import com.fasterxml.jackson.databind.ser.impl.SimpleBeanPropertyFilter;
import com.fasterxml.jackson.databind.ser.impl.SimpleFilterProvider;
import com.google.common.collect.Lists;
import com.theotherian.jackson.dto.Thing;
import com.theotherian.jackson.dto.User;
import com.theotherian.jackson.mixin.ThingMixin;

public class SerializationTest {
  
  @Test
  public void failure() throws Exception {
    User user = createUser();
    ObjectMapper mapper = new ObjectMapper();
    
    StringWriter writer = new StringWriter();
    mapper.writeValue(writer, user);
  }
  
  @Test
  public void success() throws Exception {
    User user = createUser();
    ObjectMapper mapper = new ObjectMapper();
    mapper.addMixInAnnotations(Thing.class, ThingMixin.class);
    FilterProvider filterProvider = new SimpleFilterProvider()
      .addFilter("thing filter", SimpleBeanPropertyFilter.serializeAllExcept("user"));
    mapper.setFilters(filterProvider);
    
    StringWriter writer = new StringWriter();
    mapper.writeValue(writer, user);
  }

  private User createUser() {
    User user = new User();
    user.setName("me");
    Thing thing = new Thing();
    thing.setName("that");
    thing.setUser(user);
    user.setThings(Lists.newArrayList(thing));
    return user;
  }

}

successful-serialization

{"id":1,"name":"my widget"}

Thing.java

package com.theotherian.jackson.dto;

public class Thing {

  private String name;
  
  public String getName() { return name; }
  public void setName(String name) { this.name = name; }
  
  private User user;
  
  public User getUser() { return user; }
  public void setUser(User user) { this.user = user; }
}

ThingMixin.java

package com.theotherian.jackson.mixin;

import com.fasterxml.jackson.annotation.JsonFilter;

@JsonFilter("thing filter")
public class ThingMixin {

}

unserializable-field-output

{"id":1,"name":{}}

User.java

package com.theotherian.jackson.dto;

import java.util.List;

public class User {
  
  private String name;
  
  public String getName() { return name; }
  public void setName(String name) { this.name = name; }
  
  private List<Thing> things;
  
  public List<Thing> getThings() { return things; }
  public void setThings(List<Thing> things) { this.things = things; }

}

Widget.java

package com.theotherian.jackson.dto;

public class Widget {
  
  private long id;
  
  public long getId() { return id; }
  public void setId(long id) { this.id = id; }

  private WidgetName name;
  
  public WidgetName getName() { return name; }
  public void setName(WidgetName name) { this.name = name; }

}

WidgetName.java

package com.theotherian.jackson.dto;

public class WidgetName {
  
  private String value;
  
  public String value() { return value; }
  public void value(String value) { this.value = value; }

}

WidgetNameSerializer.java

package com.theotherian.jackson.serializer;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.theotherian.jackson.dto.WidgetName;

public class WidgetNameSerializer extends JsonSerializer<WidgetName> {

  @Override
  public void serialize(WidgetName widgetName, JsonGenerator jgen, SerializerProvider provider) throws IOException,
      JsonProcessingException {
    jgen.writeString(widgetName.value());
  }

  
}