When Streaming a Json File with Gson's Jsonreader, Can You Dump an Object to String?
I Am Working in Java Using the Gson Library to Process a Huge Json Document. I Absolutely Cannot Load This into Memory, It Is Upwards of 8G and Will Crash the...
I am working in Java using the GSON library to process a huge JSON document.
I absolutely cannot load this into memory, it is upwards of 8G and will crash the JVM with an OOM if I try to.
So I use JsonReader to process the stream of JSON.
There are certain times when I reach a BEGIN_OBJECT that want to just dump the contents of the object to string instead of processing each individual element.
For example, I am parsing something like this:
[ { "SchemaVersion":"15.0.0.0","LibraryVersion":"16.0.7324.1200","ErrorInfo":{ "ErrorMessage":"Access denied. You do not have permission to perform this action or access this resource.","ErrorValue":null,"TraceCorrelationId":"03ab459e-7076-5000-c1a7-196f1fc54384","ErrorCode":-2147024891,"ErrorTypeName":"System.UnauthorizedAccessException" },"TraceCorrelationId":"03ab459e-7076-5000-c1a7-196f1fc54384" } ]
When I get to ErrorInfo, I just want that as a string instead of parsed out. I don't want to have to parse each piece.
So here is the code:
try (InputStream is = (InputStream)response.getEntity();
InputStreamReader inputStreamReader = new InputStreamReader(is);
JsonReader jsonReader = new JsonReader(inputStreamReader)) {
if (jsonReader.peek() != JsonToken.BEGIN_ARRAY) {
return;
}
jsonReader.beginArray();
while (jsonReader.hasNext()) {
jsonReader.beginObject(); // Start of the default object on every request
jsonReader.skipValue(); // name SchemaVersion
jsonReader.skipValue(); // value
jsonReader.skipValue(); // name LibraryVersion
jsonReader.skipValue(); // value
jsonReader.skipValue(); // name ErrorInfo
if (jsonReader.peek() == JsonToken.BEGIN_OBJECT) {
// I want to dump the upcoming object to string here
...
Is it possible to dump the contents of the json reader for a given begin object until it ends to string?
Similar question, but not quite the same: Get a dump of a section (object) of JSON
1 Answer
Special thanks to for the answer in the comments. You can use Gson.fromJson(jsonReader, Map.class) for this exact situation.
Gson gson = new Gson();
try (InputStream is = (InputStream)response.getEntity();
InputStreamReader inputStreamReader = new InputStreamReader(is);
JsonReader jsonReader = new JsonReader(inputStreamReader)) {
if (jsonReader.peek() != JsonToken.BEGIN_ARRAY) {
return;
}
jsonReader.beginArray();
while (jsonReader.hasNext()) {
Map header = gson.fromJson(jsonReader, Map.class);
if (header.get("ErrorInfo") != null) {
String errorDump = ((Map)header.get("ErrorInfo")).toString();
// Now I have the error dump I need but I also
// didn't load the entire thing into memory!
...
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