public class JsonWriter
extends java.lang.Object
implements java.io.Closeable, java.io.Flushable
JsonWriter. Each JSON
document must contain one top-level array or object. Call methods on the
writer as you walk the structure's contents, nesting arrays and objects as
necessary:
beginArray().
Write each of the array's elements with the appropriate value(java.lang.String)
methods or by nesting other arrays and objects. Finally close the array
using endArray().
beginObject().
Write each of the object's properties by alternating calls to
name(java.lang.String) with the property's value. Write property values with the
appropriate value(java.lang.String) method or by nesting other objects or arrays.
Finally close the object using endObject().
[
{
"id": 912345678901,
"text": "How do I stream JSON in Java?",
"geo": null,
"user": {
"name": "json_newb",
"followers_count": 41
}
},
{
"id": 912345678902,
"text": "@json_newb just use JsonWriter!",
"geo": [50.454722, -104.606667],
"user": {
"name": "jesse",
"followers_count": 2
}
}
]
This code encodes the above structure:
public void writeJsonStream(OutputStream out, List<Message> messages) throws IOException {
JsonWriter writer = new JsonWriter(new OutputStreamWriter(out, "UTF-8"));
writer.setIndent(" ");
writeMessagesArray(writer, messages);
writer.close();
}
public void writeMessagesArray(JsonWriter writer, List<Message> messages) throws IOException {
writer.beginArray();
for (Message message : messages) {
writeMessage(writer, message);
}
writer.endArray();
}
public void writeMessage(JsonWriter writer, Message message) throws IOException {
writer.beginObject();
writer.name("id").value(message.getId());
writer.name("text").value(message.getText());
if (message.getGeo() != null) {
writer.name("geo");
writeDoublesArray(writer, message.getGeo());
} else {
writer.name("geo").nullValue();
}
writer.name("user");
writeUser(writer, message.getUser());
writer.endObject();
}
public void writeUser(JsonWriter writer, User user) throws IOException {
writer.beginObject();
writer.name("name").value(user.getName());
writer.name("followers_count").value(user.getFollowersCount());
writer.endObject();
}
public void writeDoublesArray(JsonWriter writer, List<Double> doubles) throws IOException {
writer.beginArray();
for (Double value : doubles) {
writer.value(value);
}
writer.endArray();
}
Each JsonWriter may be used to write a single JSON stream.
Instances of this class are not thread safe. Calls that would result in a
malformed JSON string will fail with an IllegalStateException.
| Constructor and Description |
|---|
JsonWriter(java.io.Writer out)
Creates a new instance that writes a JSON-encoded stream to
out. |
| Modifier and Type | Method and Description |
|---|---|
JsonWriter |
beginArray()
Begins encoding a new array.
|
JsonWriter |
beginObject()
Begins encoding a new object.
|
void |
close()
Flushes and closes this writer and the underlying
Writer. |
JsonWriter |
endArray()
Ends encoding the current array.
|
JsonWriter |
endObject()
Ends encoding the current object.
|
void |
flush()
Ensures all buffered data is written to the underlying
Writer
and flushes that writer. |
boolean |
getSerializeNulls()
Returns true if object members are serialized when their value is null.
|
boolean |
isHtmlSafe()
Returns true if this writer writes JSON that's safe for inclusion in HTML
and XML documents.
|
boolean |
isLenient()
Returns true if this writer has relaxed syntax rules.
|
JsonWriter |
jsonValue(java.lang.String value)
Writes
value directly to the writer without quoting or
escaping. |
JsonWriter |
name(java.lang.String name)
Encodes the property name.
|
JsonWriter |
nullValue()
Encodes
null. |
void |
setHtmlSafe(boolean htmlSafe)
Configure this writer to emit JSON that's safe for direct inclusion in HTML
and XML documents.
|
void |
setIndent(java.lang.String indent)
Sets the indentation string to be repeated for each level of indentation
in the encoded document.
|
void |
setLenient(boolean lenient)
Configure this writer to relax its syntax rules.
|
void |
setSerializeNulls(boolean serializeNulls)
Sets whether object members are serialized when their value is null.
|
JsonWriter |
value(boolean value)
Encodes
value. |
JsonWriter |
value(java.lang.Boolean value)
Encodes
value. |
JsonWriter |
value(double value)
Encodes
value. |
JsonWriter |
value(long value)
Encodes
value. |
JsonWriter |
value(java.lang.Number value)
Encodes
value. |
JsonWriter |
value(java.lang.String value)
Encodes
value. |
public JsonWriter(java.io.Writer out)
out.
For best performance, ensure Writer is buffered; wrapping in
BufferedWriter if necessary.public final void setIndent(java.lang.String indent)
indent.isEmpty() the encoded document
will be compact. Otherwise the encoded document will be more
human-readable.indent - a string containing only whitespace.public final void setLenient(boolean lenient)
NaNs or infinities.
public boolean isLenient()
public final void setHtmlSafe(boolean htmlSafe)
<, >,
& and = before writing them to the stream. Without this
setting, your XML/HTML encoder should replace these characters with the
corresponding escape sequences.public final boolean isHtmlSafe()
public final void setSerializeNulls(boolean serializeNulls)
public final boolean getSerializeNulls()
public JsonWriter beginArray() throws java.io.IOException
endArray().java.io.IOExceptionpublic JsonWriter endArray() throws java.io.IOException
java.io.IOExceptionpublic JsonWriter beginObject() throws java.io.IOException
endObject().java.io.IOExceptionpublic JsonWriter endObject() throws java.io.IOException
java.io.IOExceptionpublic JsonWriter name(java.lang.String name) throws java.io.IOException
name - the name of the forthcoming value. May not be null.java.io.IOExceptionpublic JsonWriter value(java.lang.String value) throws java.io.IOException
value.value - the literal string value, or null to encode a null literal.java.io.IOExceptionpublic JsonWriter jsonValue(java.lang.String value) throws java.io.IOException
value directly to the writer without quoting or
escaping.value - the literal string value, or null to encode a null literal.java.io.IOExceptionpublic JsonWriter nullValue() throws java.io.IOException
null.java.io.IOExceptionpublic JsonWriter value(boolean value) throws java.io.IOException
value.java.io.IOExceptionpublic JsonWriter value(java.lang.Boolean value) throws java.io.IOException
value.java.io.IOExceptionpublic JsonWriter value(double value) throws java.io.IOException
value.value - a finite value. May not be NaNs or
infinities.java.io.IOExceptionpublic JsonWriter value(long value) throws java.io.IOException
value.java.io.IOExceptionpublic JsonWriter value(java.lang.Number value) throws java.io.IOException
value.value - a finite value. May not be NaNs or
infinities.java.io.IOExceptionpublic void flush()
throws java.io.IOException
Writer
and flushes that writer.flush in interface java.io.Flushablejava.io.IOExceptionpublic void close()
throws java.io.IOException
Writer.close in interface java.io.Closeableclose in interface java.lang.AutoCloseablejava.io.IOException - if the JSON document is incomplete.Copyright © 2018. All Rights Reserved.