使用Java中的Jackson解析JSON文件，并将信息一一写入单个对象 [英] Parsing JSON file using Jackson in Java and writing information one by one to an single Object
问题描述
我正在尝试将大JSON/JSON-LD文件转换为XML.JSON文件将包含事件列表(并非所有事件都相同，并且每个事件可能具有不同的信息/数据).我想一个个地读取事件，并将信息存储在一个对象中(而不是为每个事件使用不同的对象).我想以父母和孩子的形式存储它.读取一个事件后，我想将其转换为JSON，然后转到下一个事件.
I am trying to convert the large JSON/JSON-LD file to XML. The JSON file will contain a list of events (not all events are the same and each may have different information/data). I would like to read the events one by one and store the information in a single Object (rather than having different objects for each event). I would like to store it in the form of Parent and Children. As soon as I read one event I would like to convert it to JSON then go to the next one.
我正在调查JACKSON，看起来很适合.但是，我正在调查此特定类
I am looking into JACKSON and seems like it fits this. However, I am looking into this particular class TokenBuffer which is actually kind of doing the same. It's reading the JSON file line by line and then trying to see if the incoming element is Array or Object based on that it's making various decisions.
我想确认是否可以直接使用该类传递JsonFile并获取父级和子级关系，该关系将存储在 JsonWriteContext 中，以后我可以将其转换为XML.
I wanted to confirm if I can use this Class directly to pass my JsonFile and get the Parent and child relationship which will be stored in JsonWriteContext later I can convert it to XML.
基本上，我的示例文件将在JSON中包含许多事件，我想一次读取它们，然后在单个对象中获取元素信息及其父子关系，例如 HashMap .
Basically, my sample file will have many events in the JSON which I would like to read one by one and then get the element info and its parent-children relationship in a Single Object such as maybe HashMap.
推荐答案
在尝试了一些操作之后，下面是我的代码，其中包含Json的Parent和Child元素:
After trying some of the things following is my code which will contain the Parent and Child elements from Json:
@Getter
@Setter
@NoArgsConstructor
public class JsonContext {
private JsonContext parent;
private String key;
private String value;
private int childCount;
private Map<String, List<JsonContext>> children = new HashMap<String, List<JsonContext>>();
// Constructor for Children Object
JsonContext(String key, String value) {
this.key = key;
this.value = value;
}
// Constructor for Parent Object
JsonContext(JsonContext parent, String key, String value) {
this(key, value);
this.parent = parent;
}
// Add child based on incoming element
public JsonContext addChild(JsonContext context) {
List<JsonContext> childValues = children.get(context.getKey());
if (childValues == null) {
childValues = new ArrayList<JsonContext>();
}
childValues.add(context);
children.put(context.key, childValues);
childCount++;
return context;
}
// Get the parent and their subsequent children (test purpose only)
@Override
public String toString() {
String s = key + children.entrySet().stream().map(e -> e.getKey() + " -- " + String.join(", ", e.getValue().stream().map(v -> v.toString())
.collect(Collectors.toList()))).collect(Collectors.toList());
if (value.length() > 0) {
final String chars = value.toString().trim();
if (chars.length() > 0) {
s = s + " = " + chars;
}
}
return s;
}
}
以上是将存储信息的上下文文件.下面是JSON解析器文件.
The above is the context file that will store the information. Below is the JSON parser file.
import java.io.File;
import java.io.IOException;
import java.net.URISyntaxException;
import java.util.Arrays;
import com.converter.xml2jsonld.test.JSONParser;
import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
public class JsonEventsParser {
private JsonContext context = null;
private final String[] eventTypes = new String[] { "event1", "event2", "event3", "event4",
"event5" };
public void jsonFileIterator() throws URISyntaxException, JsonParseException, IOException {
// Get the JSON Factory and parser Object
JsonFactory jsonFactory = new JsonFactory();
JsonParser jsonParser = jsonFactory.createParser(new File(JSONParser.class.getClassLoader().getResource("inputJsonFile.json").toURI()));
JsonToken current = jsonParser.nextToken();
// Check the first element is Object
if (current != JsonToken.START_OBJECT) {
throw new IllegalStateException("Expected content to be an array");
}
// Call the method to loop until the end of the events file
FileNavigator(jsonParser);
}
private void FileNavigator(JsonParser jsonParser) throws IOException {
JsonToken current = jsonParser.getCurrentToken();
// Loop until the end of the EPCIS events file
while (jsonParser.nextToken() != JsonToken.END_OBJECT) {
final JsonToken token = jsonParser.nextToken();
final String name = jsonParser.getCurrentName();
// Handling the fields with direct key value pairs
if ((token == JsonToken.FIELD_NAME || token == JsonToken.VALUE_STRING)) {
writeFieldName(jsonParser, token);
}
// Handling the Object
if (token == JsonToken.START_OBJECT) {
writeObjectFields(jsonParser, token);
}
// Handling the Array
if (token == JsonToken.START_ARRAY) {
writeArrayFields(jsonParser, token);
}
if (context != null) {
if (context.getParent() != null) {
context = context.getParent();
}
}
}
System.out.println(context.getChildren().toString());
}
// Method to obtain the STRING field and write into Context
private void writeFieldName(JsonParser jsonParser, JsonToken token) throws IOException {
final String key = jsonParser.getCurrentName();
final String value = jsonParser.getValueAsString();
// Check for the eventType
if (context == null && Arrays.asList(eventTypes).contains(value)) {
context = new JsonContext(key, value);
} else if (context != null) {
context = context.addChild(new JsonContext(context, key, value));
}
}
// Method to obtain the OBJECT and write its children into Context
private void writeObjectFields(JsonParser jsonParser, JsonToken token) throws IOException {
final String objectParent = jsonParser.getCurrentName() == null ? context.getParent().getKey() : jsonParser.getCurrentName();
// Add the name of the OBJECT
if (context == null) {
context = new JsonContext(jsonParser.getCurrentName(), "Object");
} else if (context != null) {
context = context.addChild(new JsonContext(context, objectParent, "Object"));
}
token = jsonParser.nextToken();
// Loop through all elements within OBJECT and add them to its parent
while (token != JsonToken.END_OBJECT) {
final String key = jsonParser.getCurrentName();
token = jsonParser.nextToken();
// Check for incoming tokens within array and process accordingly
switch (token) {
case START_ARRAY:
writeArrayFields(jsonParser, token);
break;
case START_OBJECT:
writeObjectFields(jsonParser, token);
break;
default:
final String value = jsonParser.getText();
context = context.addChild(new JsonContext(context, key, value));
break;
// throw new RuntimeException("Object : Elements does not match the type
// (Method: writeObjectFields)");
}
context = context.getParent();
token = jsonParser.nextToken();
}
}
// Method to Obtain the ARRAY and write its children into Context
private void writeArrayFields(JsonParser jsonParser, JsonToken token) throws IOException {
final String arrayField = jsonParser.getCurrentName();
// Add the name of the ARRAY
if (context == null) {
context = new JsonContext(arrayField, "Array");
} else if (context != null) {
context = context.addChild(new JsonContext(context, arrayField, "Array"));
}
token = jsonParser.nextToken();
// Loop through all ARRAY elements
while (token != JsonToken.END_ARRAY) {
switch (token) {
case START_OBJECT:
writeObjectFields(jsonParser, token);
break;
case VALUE_STRING:
context = context.addChild(new JsonContext(context, arrayField, jsonParser.getText()));
break;
case START_ARRAY:
writeArrayFields(jsonParser, token);
break;
default:
throw new RuntimeException("Array : Elements does not match the type (Method: writeArrayFields)");
}
context = context.getParent();
token = jsonParser.nextToken();
}
}
}
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