Develop Reference

List of Json records

I have a list of json records, for instance:
[{“age”:27,”lastname”:”Robert “,”firstName”:”Rob”,”company”:”abc”},
{“age”:27,”lastname”:”Ashok “,”firstName”:”Bob”,”company”:”def”},
{“age”:27,”lastname”:”murali“,”firstName”:”Got”,”company”,”Ghori”}]
Write a method which takes lastName as parameter and based on that input I need to get only that particular record out and get it displayed

Your probleme is not well explained, you can try this solution (after correcting your string to be a real json content)
Using ObjectMapper you can read your string to transform it to an ArrayNode
public static void main(String[] args) throws IOException {
String json= "[\n" +
" {\n" +
" \"age\":27,\n" +
" \"lastname\":\"Robert \",\n" +
" \"firstName\":\"Rob\",\n" +
" \"company\":\"abc\"\n" +
" },\n" +
" {\n" +
" \"age\":27,\n" +
" \"lastname\":\"Ashok \",\n" +
" \"firstName\":\"Bob\",\n" +
" \"company\":\"def\"\n" +
" },\n" +
" {\n" +
" \"age\":27,\n" +
" \"lastname\":\"murali\",\n" +
" \"firstName\":\"Got\",\n" +
" \"company\":\"\"\n" +
" }\n" +
"]";
// example with murali
getLine(json, "murali");
}
private static String getLine(String json, String lastName) throws IOException {
ArrayNode rootNode = (ArrayNode) new ObjectMapper().readTree(json);
for(JsonNode jsonNode : rootNode) {
ObjectNode node = (ObjectNode)jsonNode;
String lastNameValue = node.get("lastname").textValue();
if(lastName.equals(lastNameValue)){
return jsonNode.toString();
}
}
return null;
}
the result for this example is :
{"age":27,"lastname":"murali","firstName":"Got","company":""}

Is there any possibility to get the currentStockLevel from this method?

I need the currentStockLevel for another void Method in java, is there any possibility to get it?
I think no, because of void right?
public void receive (int currentStock)
{
String outLine;
if (currentStockLevel > 0)
outLine = productCode;
{
outLine = ". Current Stock: " + currentStockLevel;
outLine += " Current Stock changed from " + currentStockLevel;
currentStockLevel += currentStock;
outLine += " to " + currentStockLevel;
int storeCost = wholeSalePrice * currentStockLevel;
System.out.println (productCode + ":" + " Received " + currentStockLevel + "." + " Store Cost " + "$" + storeCost + "." + " New stock level: " + currentStockLevel);
}

Java - Edit existing JSON file

Hey I was wondering if it is possible to edit an existing json I know the location off.
So lets say that the location is C:\Something.json
then how do I edit it ??.
Thanks

If you want to edit complex JSON structure I would recommend using GSON library. You can then perform the following steps :
Gson gson = new Gson();
String yourfilecontents; //read contents from File
1) read JSON File and convert it into an object structure.
YourObject obj = gson.fromJson(yourfilecontents, YourObject.class);
2) Modify the object as per your requirement.
obj.field1(newValue);
3) Convert the object into JSON
String newJson = gson.toJson(obj);
4) Write the JSON (newJson) back to the file

Your question is very unprecise, but here are some tips, you can:
Open the JSON file with your favourite notepad
Use java.io.File API to open the file
Use some JSON Java API

To transform/filter JSON, especially in case of large files, it isn't a good idea to load the whole file to memory and use object mapping at all. Prefer stream oriented parsing and generating. For example, both Gson and Jackson support such technique. To illustrate the idea I use small, fast and GC-free library https://github.com/anatolygudkov/green-jelly. I've taken a question Loop and edit json file in java The code renames all property names "div" to "b-div"
import org.green.jelly.*;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
public class Transformation {
public static void main(final String[] args) throws IOException {
final String inputContent = "{ \n" +
" \"html\":{ \n" +
" \"child\":[ \n" +
" { \n" +
" \"head\":{ \n" +
"\n" +
" }\n" +
" },\n" +
" { \n" +
" \"body\":{ \n" +
" \"child\":[ \n" +
" { \n" +
" \"div\":{ \n" +
" \"id\":\"intk\",\n" +
" \"class\":\"akagen-row b-table\",\n" +
" \"child\":[ \n" +
" { \n" +
" \"div\":{ \n" +
" \"id\":\"aaaaa\",\n" +
" \"title\":\"bbbbbbb\",\n" +
" \"class\":\"akagen-cell\"\n" +
" }\n" +
" }\n" +
" ]\n" +
" }\n" +
" },\n" +
" { \n" +
" \"div\":{ \n" +
" \"class\":\"akagen-row b-table\",\n" +
" \"child\":[ \n" +
" { \n" +
" \"div\":{ \n" +
" \"class\":\"akagen-cell\"\n" +
" }\n" +
" },\n" +
" { \n" +
" \"div\":{ \n" +
" \"class\":\"akagen-cell\"\n" +
" }\n" +
" },\n" +
" { \n" +
" \"div\":{ \n" +
" \"class\":\"akagen-cell\"\n" +
" }\n" +
" }\n" +
" ]\n" +
" }\n" +
" }\n" +
" ]\n" +
" }\n" +
" }\n" +
" ]\n" +
" }\n" +
"}";
final Reader input = new StringReader(inputContent); // replace by FileReader
final Writer output = new StringWriter(); // replace by FileWriter
final JsonGenerator generator = new JsonGenerator();
generator.setOutput(new AppendableWriter<>(output));
final JsonParser parser = new JsonParser().setListener(new JsonParserListener() {
#Override
public void onJsonStarted() {
generator.reset();
}
#Override
public void onError(final String error, final int position) {
}
#Override
public void onJsonEnded() {
generator.eoj();
}
#Override
public boolean onObjectStarted() {
generator.startObject();
return true;
}
#Override
public boolean onObjectMember(final CharSequence name) {
if ("div".contentEquals(name)) {
generator.objectMember("b-div");
} else {
generator.objectMember(name);
}
return true;
}
#Override
public boolean onObjectEnded() {
generator.endObject();
return true;
}
#Override
public boolean onArrayStarted() {
generator.startArray();
return true;
}
#Override
public boolean onArrayEnded() {
generator.startArray();
return true;
}
#Override
public boolean onStringValue(final CharSequence data) {
generator.stringValue(data);
return true;
}
#Override
public boolean onNumberValue(final JsonNumber number) {
generator.numberValue(number);
return false;
}
#Override
public boolean onTrueValue() {
generator.trueValue();
return true;
}
#Override
public boolean onFalseValue() {
generator.falseValue();
return true;
}
#Override
public boolean onNullValue() {
generator.nullValue();
return true;
}
});
final CharArrayCharSequence buffer = new CharArrayCharSequence(1024 * 8);
int length;
while ((length = input.read(buffer.getChars())) != -1) {
buffer.setLength(length);
parser.parse(buffer);
}
parser.eoj();
System.out.println(output.toString());
}
}
Performance of such lightweight technique of transformation is almost the highest in terms of both CPU utilization and memory footprint you can reach in Java (with no tricks like SIMD over JNI).

How to handle forward slash in JSON variable with Gson API

I have JSON string that needs to be converted in Java object using Google Gson library.
I am stuck in converting due to forward slash in the following JSON string.
{
"status":"200",
"results":{
"resultitems":[
{
"uri":"/document/id/e20a8dad50d91a839c50ab5f323f3df3",
"path":"Data/xyz/abcdata",
"metadata":{
"data/category/item":"yahoo/post",
"ast_id":"67677"
}
}
]
}
Indeed, for Data/category/item, I am getting a null value. How can I correctly parse it?

Just a starting note: the JSON you put in request is not a valid JSON, but can be easily fixed adding a brace (I used fixed JSON in my answer).
I suggest you to parse your JSON this way. Declare the following classes.
public class Container {
public int status;
public Results results;
#Override
public String toString() {
return "Container [status=" + status + ", results=" + results + "]";
}
}
public class Results {
public List<ResultItem> resultitems;
#Override
public String toString() {
return "Results [resultitems=" + resultitems + "]";
}
}
public class ResultItem {
String uri;
String path;
HashMap metadata;
#Override
public String toString() {
return "ResultItem [uri=" + uri + ", path=" + path + ", metadata="
+ metadata + "]";
}
}
and then call this code:
public class Q19684865 {
public static void main(String[] args) {
String json = " { "
+ " \"status\":\"200\", "
+ " \"results\":{ "
+ " \"resultitems\":[ "
+ " { "
+ " \"uri\":\"/document/id/e20a8dad50d91a839c50ab5f323f3df3\", "
+ " \"path\":\"Data/xyz/abcdata\", "
+ " \"metadata\":{ "
+ " \"data/category/item\":\"yahoo/post\", "
+ " \"ast_id\":\"67677\" "
+ " } "
+ " } "
+ " ] "
+ " } "
+ " } ";
Container c = new Gson().fromJson(json, Container.class);
System.out.println("this is the parsed json: " +c);
System.out.println("this is the property 'data/category/item': "+c.results.resultitems.get(0).metadata.get("data/category/item"));
}
and this is the result:
this is the parsed json: Container [status=200, results=Results [resultitems=[ResultItem [uri=/document/id/e20a8dad50d91a839c50ab5f323f3df3, path=Data/xyz/abcdata, metadata={data/category/item=yahoo/post, ast_id=67677}]]]]
this is the property 'data/category/item': yahoo/post
Explanation: normally you need just POJOs if you do not have particular needs, where POJO field name corresponds to the label of the JSON value. But 'data/category/item' cannot be a valid Java identifier. So I chose to parse to a Map.
A second way could be to replace in JSON string your "data/category/item" with a valid Java identifier, "data_category_item" for example or, if you can change JSON origin, do the same at the source.

Boilerpipe - How do I output JSON?

I am using boilerpipe and it seems great, but I want to output JSON. I am using the Java version and testing in NetBeans as follows:
final URL url = new URL("http://mashable.com/2012/09/26/worlds-best-father-kickstarter-calendar");
System.out.println(ArticleExtractor.INSTANCE.getText(url));
Can anyone tell me how I go about this?

Boilerpipe does not come with a JSON serializer.
You can, however, do this (assuming you already extracted all data):
public String articleTextToJson(String article, String title, String sourceUrl) {
if (null == article) {
return "{ \"error\" : { " +
" \"message\" : \"Article did not extract\", " +
" \"code\" : 1 " +
" }, " +
" \"status\" : \"error\" " +
"}";
}
return "{ \"response\" : { " +
" \"title\" : \"" + title + "\" " +
" \"content\" : \"" + article + "\", " +
" \"source\" : \"" + sourceUrl + "\" " +
" }, " +
" \"status\" : \"success\" " +
"}"
}
The tricky part will be of course getting the title...
Or better yet use some JSON serializer like JSONObject.
Hope that helps.