Java Json 到 avro 的转换
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Json to avro conversion
提问by shree11
I'm converting Json to avro. I have json data in JSONArray. So while converting it into byte array i'm facing the problem.
我正在将 Json 转换为 avro。我在 .json 中有 json 数据 JSONArray。因此，在将其转换为字节数组时，我遇到了问题。
below is my code:
下面是我的代码：
static byte [] fromJsonToAvro(JSONArray json, String schemastr) throws Exception {
ExcelToJson ejj = new ExcelToJson();
List<String> list = new ArrayList<String>();
if (json != null) {
int len = json.length();
for (int i=0;i<len;i++){
list.add(json.get(i).toString());
}
}
InputStream input = new ByteArrayInputStream(list.getBytes()); //json.toString().getBytes()
DataInputStream din = new DataInputStream(input);
.
.
.//rest of the logic
So how can i do it? How to convert JsonArray object to bytes(i.e., how to use getBytes() method for JsonArray objects). The above code giving an error at list.getBytes()and saying getBytes() is undifined for list.
那么我该怎么做呢？如何将 JsonArray 对象转换为字节（即如何对 JsonArray 对象使用 getBytes() 方法）。上面的代码给出了一个错误list.getBytes()并说 getBytes() 对于列表是 undifined。
回答by Keegan
Avro works at the record level, bound to a schema. I don't think there's such a concept as "convert this JSON fragment to bytes for an Avro field independent of any schema or record".
Avro 在记录级别工作，绑定到模式。我不认为有“将这个 JSON 片段转换为独立于任何模式或记录的 Avro 字段的字节”这样的概念。
Assuming the array is part of a larger JSON record, if you're starting with a string of the record, you could do
假设数组是更大的 JSON 记录的一部分，如果您从记录的字符串开始，您可以这样做
public static byte[] jsonToAvro(String json, String schemaStr) throws IOException {
InputStream input = null;
DataFileWriter<GenericRecord> writer = null;
Encoder encoder = null;
ByteArrayOutputStream output = null;
try {
Schema schema = new Schema.Parser().parse(schemaStr);
DatumReader<GenericRecord> reader = new GenericDatumReader<GenericRecord>(schema);
input = new ByteArrayInputStream(json.getBytes());
output = new ByteArrayOutputStream();
DataInputStream din = new DataInputStream(input);
writer = new DataFileWriter<GenericRecord>(new GenericDatumWriter<GenericRecord>());
writer.create(schema, output);
Decoder decoder = DecoderFactory.get().jsonDecoder(schema, din);
GenericRecord datum;
while (true) {
try {
datum = reader.read(null, decoder);
} catch (EOFException eofe) {
break;
}
writer.append(datum);
}
writer.flush();
return output.toByteArray();
} finally {
try { input.close(); } catch (Exception e) { }
}
}
回答by ppearcy
This discussion is likely useful:
这个讨论可能有用：
The gist is that there is a special Json schema and you can use JsonReader/Writer to get to and from that. The Json schema you should use is defined here:
要点是有一个特殊的 Json 模式，您可以使用 JsonReader/Writer 来访问和访问它。您应该使用的 Json 架构在此处定义：
https://github.com/apache/avro/blob/trunk/share/schemas/org/apache/avro/data/Json.avsc
https://github.com/apache/avro/blob/trunk/share/schemas/org/apache/avro/data/Json.avsc
