Question

我有一些代码需要一个字节数组。转换为String时，这些字节应该是有效的JSON字符串。如果不是，它将使用“Uknown”作为密钥将String转换为有效的JSON。

除了我发现的一个边缘情况外，它工作正常。如果我传递一个包含多个有效JSON字符串的String，它只解析第一个String并认为它是有效的JSON。我宁愿它评估整个String并确定它是无效的JSON，因为它是2个或更多单独的有效JSON字符串。然后，它将使单独的JSON字符串成为一个有效的JSON字符串，就像它对任何其他无效JSON的字符串一样。

我正在使用Jackson 2.8.1。

下面是一个演示此问题的小应用程序。任何帮助将不胜感激。

import java.io.IOException;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Iterator;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.JsonNodeFactory;
import com.fasterxml.jackson.databind.node.ObjectNode;

public class EnsureValidJSON {

  private static ObjectMapper objectMapper = new ObjectMapper();

  public static void main(String[] args) {

    String input = "{\"Message1\" : \"This is the first message\"}{\"Message2\" : \"This is the second message.\"}";
    System.out.println("input: " + input);

    byte[] msg = input.getBytes();
    try {
      msg = ensureMsgIsValidJson(msg);
    } catch (IOException e) {
      // Default to Unknown:Unknown
      msg = "{\"Unknown\" : \"Unknown\"}".getBytes();
    }

    System.out.println("output: " + new String(msg));
  }

  private static boolean isJSONValid(byte[] msg) {
    boolean isValid = false;
    try {
      JsonNode jsonNode = objectMapper.readTree(msg);

      // Print out the field names and their values to show that it is only parsing the first Json String.
      Iterator<String> itr = jsonNode.fieldNames();
      while (itr.hasNext()) {
        String fieldName = itr.next();
        System.out.print(fieldName + ": ");
        System.out.println(jsonNode.get(fieldName));
      }
      isValid = true;
    } catch (IOException e) {
      String err = String.format("%s is an invalid JSON message. We will attempt to make the message valid JSON. Its key will be 'Unknown'.", new String(msg));
      System.out.println(err);
    }

    return isValid;
  }

  private static byte[] ensureMsgIsValidJson(byte[] msg) throws IOException {
    if (isJSONValid(msg)) {
      return msg;
    }
    return createValidJSON(msg);

  }

  private static byte[] createValidJSON(byte[] msg) throws IOException {
    JsonFactory factory = new JsonFactory();
    try (OutputStream out = new ByteArrayOutputStream()) {
      JsonGenerator generator = factory.createGenerator(out);
      generator.writeBinary(msg);

      JsonNodeFactory nodeFactory = new JsonNodeFactory(false);
      ObjectNode validated = nodeFactory.objectNode();
      objectMapper.writeTree(generator, validated);
      validated.put("Unknown", new String(msg));
      byte[] validatedBytes = objectMapper.writeValueAsBytes(validated);
      String message = String.format("Message(%s) was successfully converted to a valid JSON message: %s", new String(msg), new String(validatedBytes));
      System.out.println(message);
      return validatedBytes;
    }
  }

}

Answer 1

我必须使用jackson JsonParser对象来计算打开和关闭大括号的数量。如果计数为0且String中没有任何内容，则其中只有一个JSON字符串。我还必须添加代码来检查值是否为数值，因为如果值的计算结果为数字，ObjectMapper的readTree方法将不会抛出IOException。

我想要编写更多代码来完成这项工作，但它确实有效：

print 'message', '\r',
print 'this new message now covers the previous'

Jackson在第一次关闭大括号后停止读取输入字符串

1 个答案: