request参数获取，参数校验，参数处理

需求：

1.post接口，需要在过滤器中进行参数校验，校验通过之后再执行方法

2.原有代码中使用x-www-form-urlencoded传参，新需求要使用json格式

3.原有代码校验过滤器使用ServletRequest.getParameter来获取参数，并将其放入ThreadLocal<OpenapiRequest>常量中进行校验

问题：

1.改用json传参之后，再过滤器中无法通过ServletRequest.getParameter来获取参数，所有参数为null，因此无法通过参数加密校验

'使用流读取参数，可以获取参数'
            BufferedReader streamReader = new BufferedReader(new InputStreamReader(request.getInputStream(), "UTF-8"));
            StringBuilder responseStrBuilder = new StringBuilder();
            String inputStr;
            while ((inputStr = streamReader.readLine()) != null) {
                responseStrBuilder.append(inputStr);
            }
            String paramString = responseStrBuilder.toString();

2.参数校验通过，但是方法接收参数出错

Caused by: org.glassfish.hk2.api.MultiException: A MultiException has 7 exceptions.  They are:
1. java.lang.IllegalStateException: The @FormParam is utilized when the content type of the request entity is not application/x-www-form-urlencoded
2. java.lang.IllegalStateException: The @FormParam is utilized when the content type of the request entity is not application/x-www-form-urlencoded
3. java.lang.IllegalStateException: The @FormParam is utilized when the content type of the request entity is not application/x-www-form-urlencoded
4. java.lang.IllegalStateException: The @FormParam is utilized when the content type of the request entity is not application/x-www-form-urlencoded
5. java.lang.IllegalStateException: The @FormParam is utilized when the content type of the request entity is not application/x-www-form-urlencoded
6. java.lang.IllegalArgumentException: While attempting to resolve the dependencies of com.seari.ztxplatform.openapi.model.OpenapiRequest errors were found
7. java.lang.IllegalStateException: Unable to perform operation: resolve on com.seari.ztxplatform.openapi.model.OpenapiRequest

　　解决方法：替换原方法的入参注解@BeanParam为@RequestBody

3.入参中普通String字段接收成功，其中一个参数data在类中定义为String，但是传参需要一个json对象，导致报错

本次响应数据:"Can not deserialize instance of java.lang.String out of START_OBJECT token
at [Source: org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$UnCloseableInputStream@c507164;
line: 5, column: 13] (through reference chain: com.seari.ztxplatform.openapi.model.OpenapiRequest[\"data\"])"

　　此时可以在传参时，将data参数按照字符串格式传，而不是json格式，可以正常调用接口。样式如

4.前端需要统一入参格式，不能单独将data以String类型传参，要求的传参格式为

　　解决方法增加一个反序列化工具

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import groovy.util.logging.Slf4j;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import org.springframework.util.ObjectUtils;

import java.io.IOException;

/**
 * 用来自定义openapiRequest中的data在反序列化时的类型
 *
 * @author liming
 * @since 2021/12/30 17:07
 */
@Component
@Slf4j
public class DataJsonDeserializer extends JsonDeserializer {
    private final Logger log = LoggerFactory.getLogger(ApiParameterFilter.class);

    @Override
    public String deserialize(JsonParser data, DeserializationContext ctxt)
            throws IOException, JsonProcessingException {

        if (ObjectUtils.isEmpty(data)) {
            return null;
        }
        String openapiData = data.toString();

        log.info((" ====> "
                + data.getText() + "，转换后的结果 ====> " + openapiData));

        return openapiData;
    }
}

　　然后再接收参数类的data字段的set方法上加上注解

    @JsonDeserialize(using = DataJsonDeserializer.class)
    public void setData(String data) {
        this.data = data;
    }

从stackoverflow看到一个类型的问题，当时答题人提到关于这个问题可以去看看jsonDeserializer相关内容，最后试了下确实可以。真的是一句话拯救了我一天的时间，感谢！

For deserializing a node that can be either a String or an Object, you could give a look to @JsonSerialize giving a custom JsonDeserializer

详见　　

https://stackoverflow.com/questions/54062469/cannot-deserialize-instance-of-java-lang-string-out-of-start-object-token