gson 无法写入JSON：JSON对象;嵌套的异常是com.fasterxml.Jackson.databind.jsonMappingException：JSON对象

14ifxucb 于 2022-11-06 发布在其他

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Spring Boot 2.5

@PostMapping("/cart/product")
    public Response addProduct(@RequestBody Map<String, Object> payloadMap) {
        logger.info("addProduct: payloadMap: " + payloadMap);
        String userName = payloadMap.get("user_name").toString();
        final Product product = new ObjectMapper().convertValue(payloadMap.get("product"), Product.class);
        int quantity = (int) payloadMap.get("quantity");
        Cart findCart = cartRepository.findByUsername(userName);
        if (findCart == null) {
            Cart cart = new Cart();
            cart.setCreated(new Date());
            cart.setUsername(userName);
            cart.addProduct(product, quantity);
            cartRepository.save(cart);
            logger.info("addProduct: success_add_product_to_new_cart: " + cart);
            return ResponseService.getSuccessResponse(GsonUtil.gson.toJsonTree(cart));
        } else {
            findCart.addProduct(product, quantity);
            logger.info("addProduct: before_save_exist_cart: " + findCart);
            cartRepository.save(findCart);
            logger.info("addProduct: success_add_product_to_exist_cart: " + findCart);
            return ResponseService.getSuccessResponse(GsonUtil.gson.toJsonTree(findCart));
        }
    }

public class ResponseService {
    private static final int SUCCESS_CODE = 0;
    private static final String SUCCESS_MESSAGE = "Success";
    private static final int ERROR_CODE = -1;

    private static Logger logger = LogManager.getLogger(ResponseService.class);

    public static Response getSuccessResponse(JsonElement body) {
        Response response = new Response(SUCCESS_CODE, SUCCESS_MESSAGE, body);
        logger.info("getSuccessResponse: response = " + response);
        return response;
    }

import com.google.gson.JsonElement;

public class Response {
    private int code;
    private String message;
    private JsonElement body;

    public Response(int code, String message) {
        this.code = code;
        this.message = message;
    }

    public Response(int code, String message, JsonElement body) {
        this.code = code;
        this.message = message;
        this.body = body;
    }

但我在尝试返回响应时得到错误：

2020-04-12 12:02:18.825  INFO 9584 --- [nio-8092-exec-1] r.o.s.e.controllers.CartController       : addProduct: success_add_product_to_new_cart: Cart{id=130, username='admin@admin.com', created=Sun Apr 12 12:02:18 EEST 2020, updated=null, productEntities=[
ProductEntity{id=131, created=Sun Apr 12 12:02:18 EEST 2020, updated=null, quantity=1, orders=null, product=
Product{id=132, name='product name', description='product description', created=Tue Mar 10 22:34:15 EET 2020, updated=null, price=11.15, currency='EUR', images=[http://www.gravatar.com/avatar/44444?s=200x200&d=identicon, http://www.gravatar.com/avatar/33333?s=200x200&d=identicon]}}], totalAmount=11.15, currency='EUR'}
2020-04-12 12:02:18.836  INFO 9584 --- [nio-8092-exec-1] r.o.s.e.service.ResponseService          : getSuccessResponse: response = Response{code = 0, message = 'Success', body = '{"id":130,"username":"admin@admin.com","created":"Apr 12, 2020, 12:02:18 PM","productEntities":[{"id":131,"created":"Apr 12, 2020, 12:02:18 PM","quantity":1,"product":{"id":132,"name":"product name","description":"product description","created":"Mar 10, 2020, 10:34:15 PM","price":11.15,"currency":"EUR","images":["http://www.gravatar.com/avatar/44444?s=200x200&d=identicon","http://www.gravatar.com/avatar/33333?s=200x200&d=identicon"]}}],"totalAmount":11.15,"currency":"EUR"}'}
2020-04-12 12:02:18.861  WARN 9584 --- [nio-8092-exec-1] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: JsonObject; nested exception is com.fasterxml.jackson.databind.JsonMappingException: JsonObject (through reference chain: ru.otus.software_architect.eshop_orders.api.Response["body"]->com.google.gson.JsonObject["asBoolean"])]

Gson

来源：https://stackoverflow.com/questions/61169128/could-not-write-json-jsonobject-nested-exception-is-com-fasterxml-jackson-data

3条答案

按热度按时间

bfrts1fy1#

Sping Boot 默认使用Jackson来序列化json。在Response对象中，你有字段JsonElement body。它是来自gson包的对象，jackson不知道如何序列化它。
解决方案：添加属性（在application.properties文件中）以使用gson而不是Jackson。请注意，Sping Boot 版本很重要。
Spring Boot 〉= 2.3.0。版本：spring.mvc.converters.preferred-json-mapper=gson
Spring Boot 〈2.3.0。版本：spring.http.converters.preferred-json-mapper=gson
更多信息：
Configuring Spring Boot to use Gson instead of Jackson
Spring Boot 2.3 Release Notes

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ffvjumwh2#

Application.properties

spring.mvc.converters.preferred-json-mapper=gson

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nzkunb0c3#

我找到了一个变通办法，保留Jackson，但为导致Jackson序列化问题的类实现我自己的序列化程序。
这是一个黑客式的解决方案，但它现在工作。

public class GSONObjectSerializer extends SimpleSerializers {

private static final long serialVersionUID = -8745250727467996655L;

private class EmptySerializer extends StdSerializer<Object> {

    /**
     * 
     */
    private static final long serialVersionUID = 5435498165882848947L;

    protected EmptySerializer(Class t) {
        super(t);
    }

    @Override
    public void serialize(Object value, JsonGenerator gen, SerializerProvider provider) throws IOException {
        // --> Will write an empty JSON string
        gen.writeStartObject();
        gen.writeEndObject();
    }
}

@Override
public JsonSerializer<?> findSerializer(SerializationConfig config, JavaType type, BeanDescription beanDesc) {

    // --> Here is to setup which class will be serialised by the custom serializer.
    if (type.isTypeOrSubTypeOf(JsonObject.class) || type.isTypeOrSubTypeOf(StripeResponse.class)) {
        return new EmptySerializer(type.getRawClass());
    }
    return super.findSerializer(config, type, beanDesc);
}

}
您可以像这样注册您的序列化程序

@Configuration
public class SerialisationConfig {
    @Bean
    public ObjectMapper createMapper() {
        SimpleModule simpleModule = new SimpleModule();
        simpleModule.setSerializers(new GSONObjectSerializer());
        return  Jackson2ObjectMapperBuilder.json().modules(Arrays.asList(simpleModule)).build();
    }
}

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我来回答

gson 无法写入JSON：JSON对象;嵌套的异常是com.fasterxml.Jackson.databind.jsonMappingException：JSON对象

3条答案

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