无法在Java中读取json文件

Question

I am using eclipse for reading a jsonfile. I put the jsonfile in my src->main->java->testjson->jsonfile.json . Now I am trying to read the jsonfile. But my progam cannot find the file. I get the output "nothing". Here is the code I already implement:

JsonParser parser = new JSONParser();
try{

Object obj = parser.parse(new FileReader("jsonfile.json"));
JSONObject jsonObject = (JSONObject) obj;
String name = (String) jsonObject.get("name");

}

catch(Exception e){
System.out.println("nothing");
}

Answer 1

As you're saying that you use Eclipse, i assume you also run your code via Eclipse. As a default, the working directory when executing a Java program in Eclipse is the root folder of the project. Therefore, I suggest to put your jsonfile.json in the root folder of your project instead of src/main/... .

Furthermore, you should not catch Exception . Catch more specific like IOException or JSONException and then print the exception message ( e.getMessage() ), then it is much easier to solve the problem.

Answer 2

Your file within the project is called a "resource", which will be bundled in the resulting jar -file.

In maven projects such files resides in a special folder resources (like src/main/resources/testjson/jsonfile.json ), in many other project types, these files are located directly beneath the java files.

Therefore you cannot read it with FileReader , because it will not be a regular file, but zipped inside the jar file.

All you have to do is to read the file with this.getClass().getResourceAsStream("/testjson/jsonfile.json") .

Your parser should be capable to read from an InputStream instead of a Reader . If not, utilize an InputStreamReader with the correct encoding (JSON files should be UTF-8, but that depends...)

Code:

 try (InputStream is = this.getClass().getResourceAsStream("/testjson/jsonfile.json"); ) {
     Object obj = parser.parse(is); 
 } catch (Exception ex) {
     System.out.println("failed to read: "+ex.getMessage());
 }

Code if parser does not support InputStream :

 try (InputStream is = this.getClass().getResourceAsStream("/testjson/jsonfile.json"); 
     Reader rd = new InputStreamReader(is, "UTF-8"); ) {
     Object obj = parser.parse(rd); 
 } catch (Exception ex) {
     System.out.println("failed to read: "+ex.getMessage());
 }

Answer 3

Give the full path to the JSON file instead of the file name.

If the file path is home/src/main/java/testjson/jsonfile.json

String path = "home/src/main/java/testjson/jsonfile.json";
Object obj = parser.parse(new FileReader(path));