com.cedarsoftware.util.io

Class JsonWriter

java.lang.Object

com.cedarsoftware.util.io.JsonWriter

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

public class JsonWriter
extends Object
implements Closeable, Flushable

Output a Java object graph in JSON format. This code handles cyclic references and can serialize any Object graph without requiring a class to be 'Serializeable' or have any specific methods on it.

• Call the static method: JsonWriter.toJson(employee). This will convert the passed in 'employee' instance into a JSON String.
• Using streams:

       JsonWriter writer = new JsonWriter(stream);
       writer.write(employee);
       writer.close();

  This will write the 'employee' object to the passed in OutputStream.

That's it. This can be used as a debugging tool. Output an object graph using the above code. You can copy that JSON output into this site which formats it with a lot of whitespace to make it human readable: http://jsonformatter.curiousconcept.com



This will output any object graph deeply (or null). Object references are properly handled. For example, if you had A->B, B->C, and C->A, then A will be serialized with a B object in it, B will be serialized with a C object in it, and then C will be serialized with a reference to A (ref), not a redefinition of A.

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.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	JsonWriter.BigDecimalWriter
static class	JsonWriter.BigIntegerWriter
static class	JsonWriter.CalendarWriter
static class	JsonWriter.ClassWriter
static class	JsonWriter.DateWriter
static interface	JsonWriter.JsonClassWriter
static class	JsonWriter.JsonStringWriter
static class	JsonWriter.LocaleWriter
static class	JsonWriter.StringBufferWriter
static class	JsonWriter.StringBuilderWriter
static class	JsonWriter.TimestampWriter
static class	JsonWriter.TimeZoneWriter

Field Summary

Fields

Modifier and Type	Field and Description
static String	DATE_FORMAT
static String	ISO_DATE_FORMAT
static String	ISO_DATE_TIME_FORMAT
static String	PRETTY_PRINT
static String	TYPE

Constructor Summary

Constructors

Constructor and Description
JsonWriter(OutputStream out)
JsonWriter(OutputStream out, Map<String,Object> optionalArgs)

Method Summary

Methods

Modifier and Type	Method and Description
static void	addNotCustomWriter(Class c)
static void	addWriter(Class c, JsonWriter.JsonClassWriter writer)
void	close()
void	flush()
static String	formatJson(String json) Format the passed in JSON string in a nice, human readable format.
static int	getDistance(Class a, Class b)
boolean	isPrettyPrint()
static String	objectToJson(Object item)
static String	objectToJson(Object item, Map<String,Object> optionalArgs) Convert a Java Object to a JSON String.
static String	toJson(Object item) Deprecated.
static String	toJson(Object item, Map<String,Object> optionalArgs) Deprecated.
void	write(Object obj)
boolean	writeArrayElementIfMatching(Class arrayComponentClass, Object o, boolean showType, Writer out)
boolean	writeIfMatching(Object o, boolean showType, Writer out)
static void	writeJsonUtf8String(String s, Writer out) Write out special characters "\b, \f, \t, \n, \r", as such, backslash as \\ quote as \" and values less than an ASCII space (20hex) as "\\u00xx" format, characters in the range of ASCII space to a '~' as ASCII, and anything higher in UTF-8.

Methods inherited from class java.lang.Object

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

Field Detail

DATE_FORMAT

public static final String DATE_FORMAT

See Also:

Constant Field Values

ISO_DATE_FORMAT

public static final String ISO_DATE_FORMAT

See Also:

Constant Field Values

ISO_DATE_TIME_FORMAT

public static final String ISO_DATE_TIME_FORMAT

See Also:

Constant Field Values

TYPE

public static final String TYPE

See Also:

Constant Field Values

PRETTY_PRINT

public static final String PRETTY_PRINT

See Also:

Constant Field Values

Constructor Detail

JsonWriter

public JsonWriter(OutputStream out)
           throws IOException

Throws:

IOException

See Also:

JsonWriter(java.io.OutputStream, java.util.Map)

JsonWriter

public JsonWriter(OutputStream out,
          Map<String,Object> optionalArgs)
           throws IOException

Parameters:

out - OutputStream to which the JSON output will be written.

optionalArgs - (optional) Map of extra arguments indicating how dates are formatted, what fields are written out (optional). For Date parameters, use the public static DATE_TIME key, and then use the ISO_DATE or ISO_DATE_TIME indicators. Or you can specify your own custom SimpleDateFormat String, or you can associate a SimpleDateFormat object, in which case it will be used. This setting is for both java.util.Date and java.sql.Date. If the DATE_FORMAT key is not used, then dates will be formatted as longs. This long can be turned back into a date by using 'new Date(longValue)'.

Throws:

IOException

Method Detail

toJson

@Deprecated
public static String toJson(Object item)

Deprecated.

toJson

@Deprecated
public static String toJson(Object item,
                       Map<String,Object> optionalArgs)

Deprecated.

objectToJson

public static String objectToJson(Object item)
                           throws IOException

Throws:

IOException

See Also:

objectToJson(Object, java.util.Map)

objectToJson

public static String objectToJson(Object item,
                  Map<String,Object> optionalArgs)
                           throws IOException

Convert a Java Object to a JSON String.

Parameters:

item - Object to convert to a JSON String.

optionalArgs - (optional) Map of extra arguments indicating how dates are formatted, what fields are written out (optional). For Date parameters, use the public static DATE_TIME key, and then use the ISO_DATE or ISO_DATE_TIME indicators. Or you can specify your own custom SimpleDateFormat String, or you can associate a SimpleDateFormat object, in which case it will be used. This setting is for both java.util.Date and java.sql.Date. If the DATE_FORMAT key is not used, then dates will be formatted as longs. This long can be turned back into a date by using 'new Date(longValue)'.

Returns:

String containing JSON representation of passed in object.

Throws:

IOException - If an I/O error occurs

formatJson

public static String formatJson(String json)
                         throws IOException

Format the passed in JSON string in a nice, human readable format.

Parameters:

json - String input JSON

Returns:

String containing equivalent JSON, formatted nicely for human readability.

Throws:

IOException

isPrettyPrint

public boolean isPrettyPrint()

getDistance

public static int getDistance(Class a,
              Class b)

writeIfMatching

public boolean writeIfMatching(Object o,
                      boolean showType,
                      Writer out)
                        throws IOException

Throws:

IOException

writeArrayElementIfMatching

public boolean writeArrayElementIfMatching(Class arrayComponentClass,
                                  Object o,
                                  boolean showType,
                                  Writer out)
                                    throws IOException

Throws:

IOException

addWriter

public static void addWriter(Class c,
             JsonWriter.JsonClassWriter writer)

addNotCustomWriter

public static void addNotCustomWriter(Class c)

write

public void write(Object obj)
           throws IOException

Throws:

IOException

writeJsonUtf8String

public static void writeJsonUtf8String(String s,
                       Writer out)
                                throws IOException

Write out special characters "\b, \f, \t, \n, \r", as such, backslash as \\ quote as \" and values less than an ASCII space (20hex) as "\\u00xx" format, characters in the range of ASCII space to a '~' as ASCII, and anything higher in UTF-8.

Parameters:

s - String to be written in utf8 format on the output stream.

Throws:

IOException - if an error occurs writing to the output stream.

flush

public void flush()

Specified by:

flush in interface Flushable

close

public void close()

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable