使用Jackson Mixins处理第三方类JSON反序列化冲突：忽略特定字段

import java.util.List;
import java.util.ArrayList;
import java.util.Collections;

class Result {
  private List<String> ids;

  public Result() {
    this.ids = new ArrayList<>();
  }

  public List<String> getIds() {
    return ids;
  }

  public void setIds(List<String> ids) {
    this.ids = ids;
  }

  // 辅助方法，可能导致反序列化冲突
  public String getId() {
    return this.ids.isEmpty() ? null : this.ids.get(0);
  }

  public void setId(String id) {
    this.ids = (id == null) ? new ArrayList<>() : new ArrayList<>(Collections.singletonList(id));
  }

  @Override
  public String toString() {
    return "Result{" +
        "ids=" + ids +
        '}';
  }
}

{
  "ids": ["1", "2", "3"],
  "id": "1"
}

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties({ "id" })
public abstract class ResultMixin {
  // 无需包含任何字段或方法，除非你需要覆盖或添加其他注解
}

import com.fasterxml.jackson.databind.ObjectMapper;

public class JacksonMixinExample {

  public static void main(String[] args) throws Exception {
    // 1. 创建ObjectMapper实例
    ObjectMapper objectMapper = new ObjectMapper();

    // 2. 注册Mixin：将ResultMixin的注解应用到Result类
    objectMapper.addMixIn(Result.class, ResultMixin.class);

    // 3. 待反序列化的JSON字符串
    String jsonInput = "{\"ids\": [\"1\", \"2\", \"3\"], \"id\": \"1\"}";

    // 4. 执行反序列化
    Result result = objectMapper.readValue(jsonInput, Result.class);

    // 5. 验证结果
    System.out.println("反序列化后的Result对象: " + result);
    System.out.println("ids列表: " + result.getIds());
    // 预期输出: ids列表: [1, 2, 3]
  }
}

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

// 模拟第三方类，我们无法修改它
class Result {
  private List<String> ids;

  public Result() {
    this.ids = new ArrayList<>();
  }

  public List<String> getIds() {
    return ids;
  }

  public void setIds(List<String> ids) {
    System.out.println("调用 setIds: " + ids); // 用于观察调用顺序
    this.ids = ids;
  }

  // 辅助方法，可能导致反序列化冲突
  public String getId() {
    return this.ids.isEmpty() ? null : this.ids.get(0);
  }

  public void setId(String id) {
    System.out.println("调用 setId: " + id); // 用于观察调用顺序
    this.ids = (id == null) ? new ArrayList<>() : new ArrayList<>(Collections.singletonList(id));
  }

  @Override
  public String toString() {
    return "Result{" +
        "ids=" + ids +
        '}';
  }
}

// Jackson Mixin接口，用于为Result类添加注解
@JsonIgnoreProperties({ "id" })
abstract class ResultMixin {
  // 此处无需任何实现，仅用于承载注解
}

public class JacksonDeserializationWithMixin {

  public static void main(String[] args) throws Exception {
    ObjectMapper objectMapper = new ObjectMapper();

    // 注册Mixin：告诉ObjectMapper，处理Result类时，请参考ResultMixin上的注解
    objectMapper.addMixIn(Result.class, ResultMixin.class);

    String jsonInput = "{\"ids\": [\"1\", \"2\", \"3\"], \"id\": \"1\"}";

    System.out.println("原始JSON输入: " + jsonInput);
    Result result = objectMapper.readValue(jsonInput, Result.class);

    System.out.println("\n--- 反序列化结果 ---");
    System.out.println("反序列化后的Result对象: " + result);
    System.out.println("ids列表内容: " + result.getIds());
    System.out.println("ids列表大小: " + result.getIds().size());

    // 验证结果
    assert result.getIds().size() == 3 : "ids列表大小不正确";
    assert result.getIds().contains("1") && result.getIds().contains("2") && result.getIds().contains("3") : "ids列表内容不正确";
    System.out.println("反序列化成功，ids列表内容符合预期。");
  }
}

原始JSON输入: {"ids": ["1", "2", "3"], "id": "1"}
调用 setIds: [1, 2, 3]

--- 反序列化结果 ---
反序列化后的Result对象: Result{ids=[1, 2, 3]}
ids列表内容: [1, 2, 3]
ids列表大小: 3
反序列化成功，ids列表内容符合预期。