com.cedarsoftware.util.io

Class JsonReader

java.lang.Object

com.cedarsoftware.util.io.JsonReader

All Implemented Interfaces:

Closeable, AutoCloseable

public class JsonReader
extends Object
implements Closeable

Read an object graph in JSON format and make it available in Java objects, or in a "Map of Maps." (untyped representation). This code handles cyclic references and can deserialize any Object graph without requiring a class to be 'Serializeable' or have any specific methods on it. It will handle classes with non public constructors.

Usages:

• Call the static method: JsonReader.objectToJava(String json). This will return a typed Java object graph.
• Call the static method: JsonReader.jsonToMaps(String json). This will return an untyped object representation of the JSON String as a Map of Maps, where the fields are the Map keys, and the field values are the associated Map's values. You can call the JsonWriter.objectToJava() method with the returned Map, and it will serialize the Graph into the identical JSON stream from which it was read.
• Instantiate the JsonReader with an InputStream: JsonReader(InputStream in) and then call readObject(). Cast the return value of readObject() to the Java class that was the root of the graph.
• Instantiate the JsonReader with an InputStream: JsonReader(InputStream in, true) and then call readObject(). The return value will be a Map of Maps.

Author:

John DeRegnaucourt ([email protected])
Copyright (c) John DeRegnaucourt

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	JsonReader.BigDecimalReader
static class	JsonReader.BigIntegerReader
static class	JsonReader.CalendarReader
static interface	JsonReader.ClassFactory
static class	JsonReader.ClassReader
static class	JsonReader.CollectionFactory Use to create new instances of collection interfaces (needed for empty collections)
static class	JsonReader.DateReader
static interface	JsonReader.JsonClassReader
static class	JsonReader.LocaleReader
static class	JsonReader.MapFactory Use to create new instances of Map interfaces (needed for empty Maps)
static class	JsonReader.SqlDateReader
static class	JsonReader.StringBufferReader
static class	JsonReader.StringBuilderReader
static class	JsonReader.StringReader
static class	JsonReader.TimestampReader
static class	JsonReader.TimeZoneReader

Field Summary

Fields

Modifier and Type	Field and Description
static int	MAX_CODE_POINT
static char	MIN_HIGH_SURROGATE
static char	MIN_LOW_SURROGATE
static int	MIN_SUPPLEMENTARY_CODE_POINT

Constructor Summary

Constructors

Constructor and Description
JsonReader()
JsonReader(InputStream in)
JsonReader(InputStream in, boolean noObjects)

Method Summary

Methods

Modifier and Type	Method and Description
static void	addNotCustomReader(Class c)
static void	addReader(Class c, JsonReader.JsonClassReader reader)
static void	assignInstantiator(Class c, JsonReader.ClassFactory factory) For difficult to instantiate classes, you can add your own ClassFactory which will be called when the passed in class 'c' is encountered.
void	close()
Object	jsonObjectsToJava(JsonObject root) Convert a root JsonObject that represents parsed JSON, into an actual Java object.
static Object	jsonToJava(String json) Convert the passed in JSON string into a Java object graph.
static Map	jsonToMaps(String json) Convert the passed in JSON string into a Java object graph that consists solely of Java Maps where the keys are the fields and the values are primitives or other Maps (in the case of objects).
protected Object	readIfMatching(Object o, Class compType, LinkedList<JsonObject<String,Object>> stack)
Object	readObject() Finite State Machine (FSM) used to parse the JSON input into JsonObject's (Maps).
static Object	toJava(String json) Convert the passed in JSON string into a Java object graph.
static Map	toMaps(String json) Convert the passed in JSON string into a Java object graph that consists solely of Java Maps where the keys are the fields and the values are primitives or other Maps (in the case of objects).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MAX_CODE_POINT

public static final int MAX_CODE_POINT

See Also:

Constant Field Values

MIN_SUPPLEMENTARY_CODE_POINT

public static final int MIN_SUPPLEMENTARY_CODE_POINT

See Also:

Constant Field Values

MIN_LOW_SURROGATE

public static final char MIN_LOW_SURROGATE

See Also:

Constant Field Values

MIN_HIGH_SURROGATE

public static final char MIN_HIGH_SURROGATE

See Also:

Constant Field Values

Constructor Detail

JsonReader

public JsonReader()

JsonReader

public JsonReader(InputStream in)

JsonReader

public JsonReader(InputStream in,
          boolean noObjects)

Method Detail

assignInstantiator

public static void assignInstantiator(Class c,
                      JsonReader.ClassFactory factory)

For difficult to instantiate classes, you can add your own ClassFactory which will be called when the passed in class 'c' is encountered. Your ClassFactory will be called with newInstance(c) and your factory is expected to return a new instance of 'c'. This API is an 'escape hatch' to allow ANY object to be instantiated by JsonReader and is useful when you encounter a class that JsonReader cannot instantiate using its internal exhausting attempts (trying all constructors, varying arguments to them, etc.)

addReader

public static void addReader(Class c,
             JsonReader.JsonClassReader reader)

addNotCustomReader

public static void addNotCustomReader(Class c)

readIfMatching

protected Object readIfMatching(Object o,
                    Class compType,
                    LinkedList<JsonObject<String,Object>> stack)
                         throws IOException

Throws:

IOException

toJava

public static Object toJava(String json)

Convert the passed in JSON string into a Java object graph.

Parameters:

json - String JSON input

Returns:

Java object graph matching JSON input, or null if an error occurred.

jsonToJava

public static Object jsonToJava(String json)
                         throws IOException

Convert the passed in JSON string into a Java object graph.

Parameters:

json - String JSON input

Returns:

Java object graph matching JSON input

Throws:

IOException - If an I/O error occurs

toMaps

public static Map toMaps(String json)

Convert the passed in JSON string into a Java object graph that consists solely of Java Maps where the keys are the fields and the values are primitives or other Maps (in the case of objects).

Parameters:

json - String JSON input

Returns:

Java object graph of Maps matching JSON input, or null if an error occurred.

jsonToMaps

public static Map jsonToMaps(String json)
                      throws IOException

Convert the passed in JSON string into a Java object graph that consists solely of Java Maps where the keys are the fields and the values are primitives or other Maps (in the case of objects).

Parameters:

json - String JSON input

Returns:

Java object graph of Maps matching JSON input, or null if an error occurred.

Throws:

IOException - If an I/O error occurs

readObject

public Object readObject()
                  throws IOException

Finite State Machine (FSM) used to parse the JSON input into JsonObject's (Maps). Then, if requested, the JsonObjects are converted into Java instances.

Returns:

Java Object graph constructed from InputStream supplying JSON serialized content.

Throws:

IOException - for stream errors or parsing errors.

jsonObjectsToJava

public Object jsonObjectsToJava(JsonObject root)
                         throws IOException

Convert a root JsonObject that represents parsed JSON, into an actual Java object.

Parameters:

root - JsonObject instance that was the root object from the JSON input that was parsed in an earlier call to JsonReader.

Returns:

a typed Java instance that was serialized into JSON.

Throws:

IOException

close

public void close()

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable