JsonParser (JSON Documentation)

All Superinterfaces:

java.lang.AutoCloseable, java.io.Closeable
```
public interface JsonParser
extends java.io.Closeable
```
Provides forward, read-only access to JSON data in a streaming way. This is the most efficient way for reading JSON data. The class Json contains methods to create parsers from input sources (InputStream and Reader).
The following example demonstrates how to create a parser from a string that contains an empty JSON array:
```
 
 JsonParser parser = Json.createParser(new StringReader("[]"));
 
 
```
The class JsonParserFactory also contains methods to create JsonParser instances. JsonParserFactory is preferred when creating multiple parser instances. A sample usage is shown in the following example:
```
 
 JsonParserFactory factory = Json.createParserFactory();
 JsonParser parser1 = factory.createParser(...);
 JsonParser parser2 = factory.createParser(...);
 
 
```
JsonParser parses JSON using the pull parsing programming model. In this model the client code controls the thread and calls the method next() to advance the parser to the next state after processing each element. The parser can generate the following events: START_OBJECT, END_OBJECT, START_ARRAY, END_ARRAY, KEY_NAME, VALUE_STRING, VALUE_NUMBER, VALUE_TRUE, VALUE_FALSE, and VALUE_NULL.
For example, for an empty JSON object ({ }), the parser generates the event START_OBJECT with the first call to the method next() and the event END_OBJECT with the second call to the method next(). The following code demonstrates how to access these events:
```
 
 Event event = parser.next(); // START_OBJECT
 event = parser.next();       // END_OBJECT
 
 
```
For example, for the following JSON:
```
 {
   "firstName": "John", "lastName": "Smith", "age": 25,
   "phoneNumber": [
       { "type": "home", "number": "212 555-1234" },
       { "type": "fax", "number": "646 555-4567" }
    ]
 }
 
```
calls to the method next() result in parse events at the specified locations below (marked in bold):
```
 {START_OBJECT
   "firstName"KEY_NAME: "John"VALUE_STRING, "lastName"KEY_NAME: "Smith"VALUE_STRING, "age"KEY_NAME: 25VALUE_NUMBER,
   "phoneNumber"KEY_NAME : [START_ARRAY
       {START_OBJECT "type"KEY_NAME: "home"VALUE_STRING, "number"KEY_NAME: "212 555-1234"VALUE_STRING }END_OBJECT,
       {START_OBJECT "type"KEY_NAME: "fax"VALUE_STRING, "number"KEY_NAME: "646 555-4567"VALUE_STRING }END_OBJECT
    ]END_ARRAY
 }END_OBJECT
 
```
The methods next() and hasNext() enable iteration over parser events to process JSON data. JsonParser provides get methods to obtain the value at the current state of the parser. For example, the following code shows how to obtain the value "John" from the JSON above:
```
 
 Event event = parser.next(); // START_OBJECT
 event = parser.next();       // KEY_NAME
 event = parser.next();       // VALUE_STRING
 parser.getString();          // "John"
 
 
```
See Also:
Json, JsonParserFactory

Nested Class Summary

Nested Classes
Modifier and Type Interface and Description

static class JsonParser.Event
An event from JsonParser.

Nested Classes
Modifier and Type	Interface and Description
`static class`	`JsonParser.Event` An event from `JsonParser`.

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`close()` Closes this parser and frees any resources associated with the parser.
`int`	`getInt()` Returns a JSON number as an integer.
`JsonLocation`	`getLocation()` Return the location that corresponds to the parser's current state in the JSON input source.
`long`	`getLong()` Returns a JSON number as a long.
`java.lang.String`	`getString()` Returns a `String` for the name in a name/value pair, for a string value or a number value.
`boolean`	`hasNext()` Returns `true` if there are more parsing states.
`boolean`	`isIntegralNumber()` Returns true if the JSON number at the current parser state is a integral number.
`JsonParser.Event`	`next()` Returns the event for the next parsing state.

- Method Detail
  - hasNext
```
boolean hasNext()
```
    Returns true if there are more parsing states. This method returns false if the parser reaches the end of the JSON text.
    
    Returns:
    true if there are more parsing states.
    
    Throws:
    
    JsonException - if an i/o error occurs (IOException would be cause of JsonException)
    
    JsonParsingException - if the parser encounters invalid JSON when advancing to next state.
  - next
```
JsonParser.Event next()
```
    Returns the event for the next parsing state.
    
    Throws:
    
    JsonException - if an i/o error occurs (IOException would be cause of JsonException)
    
    JsonParsingException - if the parser encounters invalid JSON when advancing to next state.
    
    java.util.NoSuchElementException - if there are no more parsing states.
  - getString
```
java.lang.String getString()
```
    Returns a String for the name in a name/value pair, for a string value or a number value. This method should only be called when the parser state is JsonParser.Event.KEY_NAME, JsonParser.Event.VALUE_STRING, or JsonParser.Event.VALUE_NUMBER.
    
    Returns:
    a name when the parser state is JsonParser.Event.KEY_NAME a string value when the parser state is JsonParser.Event.VALUE_STRING a number value when the parser state is JsonParser.Event.VALUE_NUMBER
    
    Throws:
    
    java.lang.IllegalStateException - when the parser state is not KEY_NAME, VALUE_STRING, or VALUE_NUMBER
  - isIntegralNumber
```
boolean isIntegralNumber()
```
    Returns true if the JSON number at the current parser state is a integral number. This integral type information can be used to invoke an appropriate accessor method to obtain a numeric value as in the following example:
```
 
 JsonParser parser = ...
 if (parser.isIntegralNumber()) {
     parser.getInt();     // or other methods to get integral value
 } else {
     parser.getString();
 }
 
 
```
    Returns:
    true if this number is a integral number, otherwise false
    
    Throws:
    
    java.lang.IllegalStateException - when the parser state is not VALUE_NUMBER
  - getInt
```
int getInt()
```
    Returns a JSON number as an integer. The returned value is equal to intValue(). Note that this conversion can lose information about the overall magnitude and precision of the number value as well as return a result with the opposite sign. This method should only be called when the parser state is JsonParser.Event.VALUE_NUMBER.
    
    Returns:
    an integer for a JSON number
    
    Throws:
    
    java.lang.IllegalStateException - when the parser state is not VALUE_NUMBER
  - getLong
```
long getLong()
```
    Returns a JSON number as a long. The returned value is equal to longValue(). Note that this conversion can lose information about the overall magnitude and precision of the number value as well as return a result with the opposite sign. This method is only called when the parser state is JsonParser.Event.VALUE_NUMBER.
    
    Returns:
    a long for a JSON number
    
    Throws:
    
    java.lang.IllegalStateException - when the parser state is not VALUE_NUMBER
  - getLocation
```
JsonLocation getLocation()
```
    Return the location that corresponds to the parser's current state in the JSON input source. The location information is only valid in the current parser state (or until the parser is advanced to a next state).
    
    Returns:
    a non-null location corresponding to the current parser state in JSON input source
  - close
```
void close()
```
    Closes this parser and frees any resources associated with the parser. This method closes the underlying input source.
    
    Specified by:
    
    close in interface java.lang.AutoCloseable
    
    Specified by:
    
    close in interface java.io.Closeable
    
    Throws:
    
    JsonException - if an i/o error occurs (IOException would be cause of JsonException)

Interface JsonParser

Nested Class Summary

Method Summary

Method Detail

hasNext

next

getString

isIntegralNumber

getInt

getLong

getLocation

close