Converting JsonValue to String

[heykirby]

Simdjson cannot compress structures
for example json
{ "field1": { "field2": "xx" } }
I cannot get the compressed value for field1, value is { "field2": "xx" }

[piotrrzysko]

Do I understand correctly that you would like to read the value of field1 as a string? Something like this:

JsonValue json = parser.parse(...);
Iterator<Map.Entry<String, JsonValue>> it = json.objectIterator();
Map.Entry<String, JsonValue> field1 = it.next();
System.out.println(field1.getValue().asString()); // this prints '{ "field2": "xx" }'

[heykirby]

yes, it looks like simdjson has implemented this capability，thanks

[andyglow]

for me field1.getValue().asString() doesn't work if the value is either <array> or <object>
gets me something like this instead

Caused by: java.lang.StringIndexOutOfBoundsException: Range [3198, 3198 + 1952541807) out of bounds for length 35651584
         at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:55)
         at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:52)
         at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:213)
         at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:210)
         at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:98)
         at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckFromIndexSize(Preconditions.java:118)
         at java.base/jdk.internal.util.Preconditions.checkFromIndexSize(Preconditions.java:397)
         at java.base/java.lang.String.checkBoundsOffCount(String.java:4849)
         at java.base/java.lang.String.<init>(String.java:522)
         at org.simdjson.JsonValue.getString(JsonValue.java:87)
         at org.simdjson.JsonValue.asString(JsonValue.java:81)

[piotrrzysko]

The snippet I provided in the previous comment was just to verify if I understand the issue correctly. I'm not saying that currently this line works according to the comment:

System.out.println(field1.getValue().asString()); // this prints '{ "field2": "xx" }'

[andyglow]

gotcha. are there plans to make asString handle these scenarios, @piotrrzysko ?
in some cases it would be great to be able to reuse original slice of buffer to stringify the value instead of building a new one traversing the value

[piotrrzysko]

I think we can try to add it. However, I'm currently busy working on #35, so I can't promise when I'll be able to do that.

[andyglow]

I see. That would be wonderful if you could make it happen at some point. I'll be waiting for it :)

[andyglow]

hello @piotrrzysko. a gentle reminder that this feature still highly anticipated and appreciated :)

[heykirby]

@andyglow refer to #59 ,it works for us，and might work for you too

[matkt]

I’m really interested in this project and was wondering if there’s been any progress on this issue or if someone is currently working on it. The ability to convert to a string would be extremely helpful.
Thanks for your hard work and for any update you can provide!

[heykirby]

I’m really interested in this project and was wondering if there’s been any progress on this issue or if someone is currently working on it. The ability to convert to a string would be extremely helpful. Thanks for your hard work and for any update you can provide!

#63 hello,it may be work for you

[piotrrzysko]

The ability to convert to a string would be extremely helpful.

Just out of curiosity: why could this feature be useful? What are the use cases?

[heykirby]

The ability to convert to a string would be extremely helpful.

Just out of curiosity: why could this feature be useful? What are the use cases?

hello，piotrrzysko，use cases can be found in #63 src/test/java/org/simdjson/demand/PathsBasedTest.java.
When constructing an instance of PathsBasedJsonParser, simply pass the path to be parsed as a constructor argument. If the corresponding path is of type map or array, it will automatically be compressed into a string. Both keys and indexes of maps and arrays are supported in the paths to be parsed
for example, json like

PathsBasedJsonParser parser = new PathsBasedJsonParser("a.b", "a.b.c", "d.[0]", "d", "d.[0].f");   
String[] values = parser.parse(json);  
// values = ["{\"c\":\"value1\"}", "value1", "{\"e\":1}", "[{\"e\":1},{\"f\":2.1}]", "2.1"]  

you can also specify the type of the value you want to parse. This is useful when you want to ensure that the value you are parsing is of a certain type, string type default if not assign.

PathsBasedJsonParser parser = new PathsBasedJsonParser( "d.[0].e:INT", "d.[0].f:DOUBLE");  
Object[] values = parser.parse(json);  
// values = [1, 2.1]. 

it's important to note that when referring to array indices, they should be enclosed within square brackets []. If a map key contains square brackets, they need to be written twice as a backslash is used to escape them.
for example,if json like this,we can get $.a.[b.c] like

PathsBasedJsonParser parser = new PathsBasedJsonParser( "a.[[b.c]]");  
String[] values = parser.parse(json);  
// values = ["value1"]. 

[andyglow]

could be useful in http proxy like scenario where only some nested (no matter how they look) parts of the input got transferred down the path

some ETL pipelines may work that way