Package com.cedarsoftware.util.io

Class 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.jsonToJava(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.objectToJson() method with the returned Map, and it will serialize the Graph into the equivalent 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) Cedar Software LLC

    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.

    • Field Detail

      • CUSTOM_READER_MAP

        public static final String CUSTOM_READER_MAP
        If set, this maps class ==> CustomReader
        See Also:
        Constant Field Values

      • NOT_CUSTOM_READER_MAP

        public static final String NOT_CUSTOM_READER_MAP
        If set, this indicates that no custom reader should be used for the specified class ==> CustomReader
        See Also:
        Constant Field Values

      • USE_MAPS

        public static final String USE_MAPS
        If set, the read-in JSON will be turned into a Map of Maps (JsonObject) representation
        See Also:
        Constant Field Values

      • UNKNOWN_OBJECT

        public static final String UNKNOWN_OBJECT
        What to do when an object is found and 'type' cannot be determined.
        See Also:
        Constant Field Values

      • FAIL_ON_UNKNOWN_TYPE

        public static final String FAIL_ON_UNKNOWN_TYPE
        Will fail JSON parsing if 'type' class defined but is not on classpath.
        See Also:
        Constant Field Values

      • JSON_READER

        public static final String JSON_READER
        Pointer to 'this' (automatically placed in the Map)
        See Also:
        Constant Field Values

      • OBJECT_RESOLVER

        public static final String OBJECT_RESOLVER
        Pointer to the current ObjectResolver (automatically placed in the Map)
        See Also:
        Constant Field Values

      • TYPE_NAME_MAP

        public static final String TYPE_NAME_MAP
        If set, this map will be used when writing @type values - allows short-hand abbreviations type names
        See Also:
        Constant Field Values

      • MISSING_FIELD_HANDLER

        public static final String MISSING_FIELD_HANDLER
        If set, this object will be called when a field is present in the JSON but missing from the corresponding class
        See Also:
        Constant Field Values

      • notCustom

        protected final Set<Class> notCustom

    • Constructor Detail

      • JsonReader

        public JsonReader()

      • JsonReader

        public JsonReader​(Map<String,​Object> optionalArgs)
        Use this constructor if you already have a JsonObject graph and want to parse it into Java objects by calling jsonReader.jsonObjectsToJava(rootJsonObject) after constructing the JsonReader.
        Parameters:
        optionalArgs - Map of optional arguments for the JsonReader.

      • JsonReader

        public JsonReader​(InputStream inp,
                  boolean useMaps)

      • JsonReader

        public JsonReader​(byte[] inp,
                  Map<String,​Object> optionalArgs)

    • Method Detail

      • isAllowNanAndInfinity

        public static boolean isAllowNanAndInfinity()
        Returns:
        boolean the allowNanAndInfinity setting

      • setAllowNanAndInfinity

        public static void setAllowNanAndInfinity​(boolean lenient)
        Set the reader to be out of RFC 4627: it will accept "NaN", "-Infinity" and "Infinity" values.
        Parameters:
        lenient - the lenient to set

      • assignInstantiator

        public static void assignInstantiator​(String n,
                                      JsonReader.Factory f)
        For difficult to instantiate classes, you can add your own ClassFactory or ClassFactoryEx 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.)
        Parameters:
        n - Class name to assign an ClassFactory to
        f - ClassFactory that will create 'c' instances

      • assignInstantiator

        public static void assignInstantiator​(Class c,
                                      JsonReader.Factory f)
        Assign instantiated by Class. Falls back to JsonReader.assignInstantiator(String, Factory)
        Parameters:
        c - Class to assign an ClassFactory to
        f - ClassFactory that will create 'c' instances

      • addReader

        public void addReader​(Class c,
                      JsonReader.JsonClassReaderBase reader)
        Call this method to add a custom JSON reader to json-io. It will associate the Class 'c' to the reader you pass in. The readers are found with isAssignableFrom(). If this is too broad, causing too many classes to be associated to the custom reader, you can indicate that json-io should not use a custom reader for a particular class, by calling the addNotCustomReader() method.
        Parameters:
        c - Class to assign a custom JSON reader to
        reader - The JsonClassReader which will read the custom JSON format of 'c'

      • addReaderPermanent

        public static void addReaderPermanent​(Class c,
                                      JsonReader.JsonClassReaderBase reader)
        Call this method to add a custom JSON reader to json-io. It will associate the Class 'c' to the reader you pass in. The readers are found with isAssignableFrom(). If this is too broad, causing too many classes to be associated to the custom reader, you can indicate that json-io should not use a custom reader for a particular class, by calling the addNotCustomReader() method. This method will add the customer reader such that it will be there permanently, for the life of the JVM (static).
        Parameters:
        c - Class to assign a custom JSON reader to
        reader - The JsonClassReader which will read the custom JSON format of 'c'

      • addNotCustomReader

        public void addNotCustomReader​(Class c)
        Force json-io to use it's internal generic approach to writing the passed in class, even if a Custom JSON reader is specified for its parent class.
        Parameters:
        c - Class to which to force no custom JSON reading to occur. Normally, this is not needed, however, if a reader is assigned to a parent class of 'c', then calling this method on 'c' will prevent any custom reader from processing class 'c'

      • getArgs

        public Map<String,​Object> getArgs()
        Returns:
        The arguments used to configure the JsonReader. These are thread local.

      • jsonToJava

        public static Object jsonToJava​(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

      • jsonToJava

        public static Object jsonToJava​(String json,
                                Map<String,​Object> optionalArgs)
        Convert the passed in JSON string into a Java object graph.
        Parameters:
        json - String JSON input
        optionalArgs - Map of optional parameters to control parsing. See readme file for details.
        Returns:
        Java object graph matching JSON input

      • jsonToJava

        public static Object jsonToJava​(InputStream inputStream,
                                Map<String,​Object> optionalArgs)
        Convert the passed in JSON string into a Java object graph.
        Parameters:
        inputStream - InputStream containing JSON input
        optionalArgs - Map of optional parameters to control parsing. See readme file for details.
        Returns:
        Java object graph matching JSON input

      • jsonToMaps

        public static Map jsonToMaps​(String json)
        Map args = ["USE_MAPS": true] Use JsonReader.jsonToJava(String json, args) Note that the return type will match the JSON type (array, object, string, long, boolean, or null). No longer recommended: Use jsonToJava with USE_MAPS:true
        Parameters:
        json - String of JSON content
        Returns:
        Map representing JSON content. Each object is represented by a Map.

      • jsonToMaps

        public static Map jsonToMaps​(String json,
                             Map<String,​Object> optionalArgs)
        Map args = ["USE_MAPS": true] Use JsonReader.jsonToJava(String json, args) Note that the return type will match the JSON type (array, object, string, long, boolean, or null). No longer recommended: Use jsonToJava with USE_MAPS:true
        Parameters:
        json - String of JSON content
        optionalArgs - Map of optional arguments to control customization. See readme file for details on these options.
        Returns:
        Map where each Map representa an object in the JSON input.

      • jsonToMaps

        public static Map jsonToMaps​(InputStream inputStream,
                             Map<String,​Object> optionalArgs)
        Map args = ["USE_MAPS": true] Use JsonReader.jsonToJava(inputStream, args) Note that the return type will match the JSON type (array, object, string, long, boolean, or null). No longer recommended: Use jsonToJava with USE_MAPS:true
        Parameters:
        inputStream - containing JSON content
        optionalArgs - Map of optional arguments to control customization. See readme file for details on these options.
        Returns:
        Map containing the content from the JSON input. Each Map represents an object from the input.

      • readObject

        public Object readObject()
        Read JSON input from the stream that was set up in the constructor, turning it into Java Maps (JsonObject's). Then, if requested, the JsonObjects can be converted into Java instances.
        Returns:
        Java Object graph constructed from InputStream supplying JSON serialized content.

      • jsonObjectsToJava

        public Object jsonObjectsToJava​(JsonObject root)
        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.

      • useMaps

        protected boolean useMaps()

      • convertParsedMapsToJava

        protected Object convertParsedMapsToJava​(JsonObject root)
        This method converts a root Map, (which contains nested Maps and so forth representing a Java Object graph), to a Java object instance. The root map came from using the JsonReader to parse a JSON graph (using the API that puts the graph into Maps, not the typed representation).
        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.

      • newInstance

        public static Object newInstance​(Class c)