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API module of JSR 374:Java API for Processing JSON
/*
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*
* Copyright (c) 2011-2013 Oracle and/or its affiliates. All rights reserved.
*
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* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
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*
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* file and include the License file at packager/legal/LICENSE.txt.
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*
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*/
package javax.json.stream;
import javax.json.JsonNumber;
import java.io.Closeable;
import java.math.BigDecimal;
/**
* Provides forward, read-only access to JSON data in a streaming way. This
* is the most efficient way for reading JSON data. The class
* {@link javax.json.Json} contains methods to create parsers from input
* sources ({@link java.io.InputStream} and {@link java.io.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 {@link JsonParserFactory} also contains methods to create
* {@code JsonParser} instances. {@link 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(...);
*
*
*
*
* {@code JsonParser} parses JSON using the pull parsing programming model.
* In this model the client code controls the thread and calls the method
* {@code next()} to advance the parser to the next state after
* processing each element. The parser can generate the following events:
* {@code START_OBJECT}, {@code END_OBJECT}, {@code START_ARRAY},
* {@code END_ARRAY}, {@code KEY_NAME}, {@code VALUE_STRING},
* {@code VALUE_NUMBER}, {@code VALUE_TRUE}, {@code VALUE_FALSE},
* and {@code VALUE_NULL}.
*
*
* For example, for an empty JSON object ({ }), the parser generates the event
* {@code START_OBJECT} with the first call to the method {@code next()} and the
* event {@code END_OBJECT} with the second call to the method {@code 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 {@code 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 {@code next()} and {@code hasNext()} enable iteration over
* parser events to process JSON data. {@code 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 javax.json.Json
* @see JsonParserFactory
* @author Jitendra Kotamraju
*/
public interface JsonParser extends /*Auto*/Closeable {
/**
* An event from {@code JsonParser}.
*/
enum Event {
/**
* Start of a JSON array. The position of the parser is after '['.
*/
START_ARRAY,
/**
* Start of a JSON object. The position of the parser is after '{'.
*/
START_OBJECT,
/**
* Name in a name/value pair of a JSON object. The position of the parser
* is after the key name. The method {@link #getString} returns the key
* name.
*/
KEY_NAME,
/**
* String value in a JSON array or object. The position of the parser is
* after the string value. The method {@link #getString}
* returns the string value.
*/
VALUE_STRING,
/**
* Number value in a JSON array or object. The position of the parser is
* after the number value. {@code JsonParser} provides the following
* methods to access the number value: {@link #getInt},
* {@link #getLong}, and {@link #getBigDecimal}.
*/
VALUE_NUMBER,
/**
* {@code true} value in a JSON array or object. The position of the
* parser is after the {@code true} value.
*/
VALUE_TRUE,
/**
* {@code false} value in a JSON array or object. The position of the
* parser is after the {@code false} value.
*/
VALUE_FALSE,
/**
* {@code null} value in a JSON array or object. The position of the
* parser is after the {@code null} value.
*/
VALUE_NULL,
/**
* End of a JSON object. The position of the parser is after '}'.
*/
END_OBJECT,
/**
* End of a JSON array. The position of the parser is after ']'.
*/
END_ARRAY
}
/**
* Returns {@code true} if there are more parsing states. This method returns
* {@code false} if the parser reaches the end of the JSON text.
*
* @return {@code true} if there are more parsing states.
* @throws javax.json.JsonException if an i/o error occurs (IOException
* would be cause of JsonException)
* @throws JsonParsingException if the parser encounters invalid JSON
* when advancing to next state.
*/
boolean hasNext();
/**
* Returns the event for the next parsing state.
*
* @throws javax.json.JsonException if an i/o error occurs (IOException
* would be cause of JsonException)
* @throws JsonParsingException if the parser encounters invalid JSON
* when advancing to next state.
* @throws java.util.NoSuchElementException if there are no more parsing
* states.
*/
Event next();
/**
* Returns a {@code 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 {@link Event#KEY_NAME}, {@link Event#VALUE_STRING},
* or {@link Event#VALUE_NUMBER}.
*
* @return a name when the parser state is {@link Event#KEY_NAME}
* a string value when the parser state is {@link Event#VALUE_STRING}
* a number value when the parser state is {@link Event#VALUE_NUMBER}
* @throws IllegalStateException when the parser state is not
* {@code KEY_NAME}, {@code VALUE_STRING}, or {@code VALUE_NUMBER}
*/
String getString();
/**
* Returns true if the JSON number at the current parser state is a
* integral number. A {@link BigDecimal} may be used to store the value
* internally and this method semantics are defined using its
* {@code scale()}. If the scale is zero, then it is considered integral
* type. 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.getBigDecimal();
* }
*
*
*
* @return true if this number is a integral number, otherwise false
* @throws IllegalStateException when the parser state is not
* {@code VALUE_NUMBER}
*/
boolean isIntegralNumber();
/**
* Returns a JSON number as an integer. The returned value is equal
* to {@code new BigDecimal(getString()).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 {@link Event#VALUE_NUMBER}.
*
* @return an integer for a JSON number
* @throws IllegalStateException when the parser state is not
* {@code VALUE_NUMBER}
* @see java.math.BigDecimal#intValue()
*/
int getInt();
/**
* Returns a JSON number as a long. The returned value is equal
* to {@code new BigDecimal(getString()).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
* {@link Event#VALUE_NUMBER}.
*
* @return a long for a JSON number
* @throws IllegalStateException when the parser state is not
* {@code VALUE_NUMBER}
* @see java.math.BigDecimal#longValue()
*/
long getLong();
/**
* Returns a JSON number as a {@code BigDecimal}. The {@code BigDecimal}
* is created using {@code new BigDecimal(getString())}. This
* method should only called when the parser state is
* {@link Event#VALUE_NUMBER}.
*
* @return a {@code BigDecimal} for a JSON number
* @throws IllegalStateException when the parser state is not
* {@code VALUE_NUMBER}
*/
BigDecimal getBigDecimal();
/**
* 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).
*
* @return a non-null location corresponding to the current parser state
* in JSON input source
*/
JsonLocation getLocation();
/**
* getJsonValue(JsonObject.class) is valid in the START_OBJECT state and
* moves the cursor to END_OBJECT.
*
* getJsonValue(JsonArray.class) is valid in the START_ARRAY state
* and moves the cursor to END_ARRAY.
*
* getJsonValue(JsonString.class) is valid in the VALUE_STRING state.
*
* getJsonValue(JsonNumber.class) is valid in the VALUE_NUMBER state.
*
* @param clazz
* @return
*
public T getJsonValue(Class clazz);
*/
/**
* Closes this parser and frees any resources associated with the
* parser. This method closes the underlying input source.
*
* @throws javax.json.JsonException if an i/o error occurs (IOException
* would be cause of JsonException)
*/
@Override
void close();
}