如何在JSON中使用oneOf并结合Jackson、jsonschema2pojo Maven插件生成Java对象并校验

{ 
  "$schema": "http://json-schema.org/draft-04/schema#", 
  "type": "object", 
  "additionalProperties": false, 
  "oneOf":[{"$ref":"request1.json#"},{"$ref":"request2.json#"}] 
}

1. 配置jsonschema2pojo Maven插件 #

要求插件版本≥1.1.1，该版本开始原生支持oneOf规则的类生成。pom.xml中插件配置参考如下：

<plugin>
  <groupId>org.jsonschema2pojo</groupId>
  <artifactId>jsonschema2pojo-maven-plugin</artifactId>
  <version>1.2.1</version>
  <configuration>
    <sourceDirectory>${project.basedir}/src/main/resources/schemas</sourceDirectory>
    <targetPackage>com.yourpackage.pojo</targetPackage>
    <includeOneOfInterface>true</includeOneOfInterface>
    <includeAdditionalProperties>false</includeAdditionalProperties>
    <useJackson>true</useJackson>
  </configuration>
  <executions>
    <execution>
      <goals>
        <goal>generate</goal>
      </goals>
    </execution>
  </executions>
</plugin>

配置说明：

• includeOneOfInterface设为true后，插件会为oneOf中指定的多个Schema对应的生成类，自动生成一个公共的父接口，根Schema对应的生成类会使用该接口作为字段类型，自动适配Request1、Request2两种结构
• includeAdditionalProperties设为false，匹配你Schema中additionalProperties=false的规则，生成的POJO不会包含额外字段的存储结构

2. 运行时校验逻辑实现 #

jsonschema2pojo仅生成POJO结构，不会自动集成oneOf的运行时校验，需要额外搭配JSON Schema校验组件实现，可按以下步骤操作：

• 引入校验依赖：

<dependency>
  <groupId>com.networknt</groupId>
  <artifactId>json-schema-validator</artifactId>
  <version>1.0.87</version>
</dependency>

• 编写校验+反序列化工具代码：

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.networknt.schema.JsonSchema;
import com.networknt.schema.JsonSchemaFactory;
import com.networknt.schema.SpecVersion;
import com.networknt.schema.ValidationMessage;
import java.util.Set;

public class RequestValidationUtils {
    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
    private static final JsonSchema ROOT_SCHEMA;

    static {
        JsonSchemaFactory factory = JsonSchemaFactory.getInstance(SpecVersion.VersionFlag.V4);
        ROOT_SCHEMA = factory.getSchema(RequestValidationUtils.class.getResourceAsStream("/schemas/root-request.json"));
    }

    public static <T> T validateAndDeserialize(String jsonStr, Class<T> clazz) throws IllegalArgumentException {
        try {
            // 先校验原始JSON匹配Schema规则
            JsonNode jsonNode = OBJECT_MAPPER.readTree(jsonStr);
            Set<ValidationMessage> errors = ROOT_SCHEMA.validate(jsonNode);
            if (!errors.isEmpty()) {
                throw new IllegalArgumentException("JSON不符合Schema规则: " + errors);
            }
            // 校验通过后再反序列化为目标POJO
            return OBJECT_MAPPER.treeToValue(jsonNode, clazz);
        } catch (Exception e) {
            throw new IllegalArgumentException("请求校验或反序列化失败: " + e.getMessage(), e);
        }
    }
}

3. 业务使用示例 #

// 传入请求JSON字符串，直接拿到校验后的POJO
RootRequest request = RequestValidationUtils.validateAndDeserialize(requestJson, RootRequest.class);
// oneOf对应的字段会自动适配为Request1或Request2的实例
if (request.getPayload() instanceof Request1) {
    // 处理Request1逻辑
} else if (request.getPayload() instanceof Request2) {
    // 处理Request2逻辑
}

内容的提问来源于stack exchange，提问作者raqm