Java Community | Help. Code. Learn.•7mo ago

jackson json question

suppose i have json array stored inside the file in the projects variable. how can i update it properly without rewriting it?

18 Replies

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Peter Rader•7mo ago

You can not update contents of a file without rewriting the contents of a file. Vice versa, if you do not change the file you do not update the file.

KoblížkáčOP•7mo ago

well then, what would be the recommended way to do that with jackson? how can i just update it

Peter Rader•7mo ago

Is it a static file?

KoblížkáčOP•7mo ago

static file?

Peter Rader•7mo ago

I mean: Are you sure the file exists?

KoblížkáčOP•7mo ago

yes

Peter Rader•7mo ago

Try

ObjectMapper om = new ObjectMapper();
var root = om.readValue(projects.toFile(), JsonNode.class);
//change the contents of the root according to your update
FileWriter fw = new FileWriter(projects.toFile());
fw.write(om.writeValueAsString(root));
fw.close();

ObjectMapper om = new ObjectMapper();
var root = om.readValue(projects.toFile(), JsonNode.class);
//change the contents of the root according to your update
FileWriter fw = new FileWriter(projects.toFile());
fw.write(om.writeValueAsString(root));
fw.close();

KoblížkáčOP•7mo ago

@Peter Rader thanks it works, any idea if Path can be converted from string with jackson?

JavaBot•7mo ago

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KoblížkáčOP•7mo ago

i want to deserialize some json to this object:

KoblížkáčOP•7mo ago

and im doing it like this:

Peter Rader•7mo ago

Hm, is this a different question?

KoblížkáčOP•7mo ago

well its unrelated to my first question do i need to make new thread

szatkus•7mo ago

I mean, Jackson could serialize Path just fine. I did it just now.

KoblížkáčOP•7mo ago

where the hell is the problem then

szatkus•7mo ago

No idea, this code works for me:

        ObjectMapper om = new ObjectMapper();
        var a = om.readValue("{\"p\":\"file:///C:/Users/basdfa/Downloads\"}", A.class);
        System.out.println(a.p);

        ObjectMapper om = new ObjectMapper();
        var a = om.readValue("{\"p\":\"file:///C:/Users/basdfa/Downloads\"}", A.class);
        System.out.println(a.p);

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