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Zabbix API library for the Java language.
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package com.zabbix4j.utils.json;
import java.io.IOException;
import java.io.Writer;
/**
* JSONWriter provides a quick and convenient way of producing JSON text.
* The texts produced strictly conform to JSON syntax rules. No whitespace is
* added, so the results are ready for transmission or storage. Each instance of
* JSONWriter can produce one JSON text.
*
* A JSONWriter instance provides a value method for appending
* values to the
* text, and a key
* method for adding keys before values in objects. There are array
* and endArray methods that make and bound array values, and
* object and endObject methods which make and bound
* object values. All of these methods return the JSONWriter instance,
* permitting a cascade style. For example,
* new JSONWriter(myWriter)
* .object()
* .key("JSON")
* .value("Hello, World!")
* .endObject(); which writes
* {"JSON":"Hello, World!"}
*
* The first method called must be array or object.
* There are no methods for adding commas or colons. JSONWriter adds them for
* you. Objects and arrays can be nested up to 20 levels deep.
*
* This can sometimes be easier than using a JSONObject to build a string.
*
* @author JSON.org
* @version 2011-11-24
*/
public class JSONWriter {
private static final int maxdepth = 200;
/**
* The object/array stack.
*/
private final JSONObject stack[];
/**
* The current mode. Values:
* 'a' (array),
* 'd' (done),
* 'i' (initial),
* 'k' (key),
* 'o' (object).
*/
protected char mode;
/**
* The writer that will receive the output.
*/
protected Writer writer;
/**
* The comma flag determines if a comma should be output before the next
* value.
*/
private boolean comma;
/**
* The stack top index. A value of 0 indicates that the stack is empty.
*/
private int top;
/**
* Make a fresh JSONWriter. It can be used to build one JSON text.
*/
public JSONWriter(Writer w) {
this.comma = false;
this.mode = 'i';
this.stack = new JSONObject[maxdepth];
this.top = 0;
this.writer = w;
}
/**
* Append a value.
*
* @param string A string value.
* @return this
* @throws com.zabbix4j.utils.json.JSONException If the value is out of sequence.
*/
private JSONWriter append(String string) throws JSONException {
if (string == null) {
throw new JSONException("Null pointer");
}
if (this.mode == 'o' || this.mode == 'a') {
try {
if (this.comma && this.mode == 'a') {
this.writer.write(',');
}
this.writer.write(string);
} catch (IOException e) {
throw new JSONException(e);
}
if (this.mode == 'o') {
this.mode = 'k';
}
this.comma = true;
return this;
}
throw new JSONException("Value out of sequence.");
}
/**
* Begin appending a new array. All values until the balancing
* endArray will be appended to this array. The
* endArray method must be called to mark the array's end.
*
* @return this
* @throws com.zabbix4j.utils.json.JSONException If the nesting is too deep, or if the object is
* started in the wrong place (for example as a key or after the end of the
* outermost array or object).
*/
public JSONWriter array() throws JSONException {
if (this.mode == 'i' || this.mode == 'o' || this.mode == 'a') {
this.push(null);
this.append("[");
this.comma = false;
return this;
}
throw new JSONException("Misplaced array.");
}
/**
* End something.
*
* @param mode Mode
* @param c Closing character
* @return this
* @throws com.zabbix4j.utils.json.JSONException If unbalanced.
*/
private JSONWriter end(char mode, char c) throws JSONException {
if (this.mode != mode) {
throw new JSONException(mode == 'a'
? "Misplaced endArray."
: "Misplaced endObject.");
}
this.pop(mode);
try {
this.writer.write(c);
} catch (IOException e) {
throw new JSONException(e);
}
this.comma = true;
return this;
}
/**
* End an array. This method most be called to balance calls to
* array.
*
* @return this
* @throws com.zabbix4j.utils.json.JSONException If incorrectly nested.
*/
public JSONWriter endArray() throws JSONException {
return this.end('a', ']');
}
/**
* End an object. This method most be called to balance calls to
* object.
*
* @return this
* @throws com.zabbix4j.utils.json.JSONException If incorrectly nested.
*/
public JSONWriter endObject() throws JSONException {
return this.end('k', '}');
}
/**
* Append a key. The key will be associated with the next value. In an
* object, every value must be preceded by a key.
*
* @param string A key string.
* @return this
* @throws com.zabbix4j.utils.json.JSONException If the key is out of place. For example, keys
* do not belong in arrays or if the key is null.
*/
public JSONWriter key(String string) throws JSONException {
if (string == null) {
throw new JSONException("Null key.");
}
if (this.mode == 'k') {
try {
this.stack[this.top - 1].putOnce(string, Boolean.TRUE);
if (this.comma) {
this.writer.write(',');
}
this.writer.write(JSONObject.quote(string));
this.writer.write(':');
this.comma = false;
this.mode = 'o';
return this;
} catch (IOException e) {
throw new JSONException(e);
}
}
throw new JSONException("Misplaced key.");
}
/**
* Begin appending a new object. All keys and values until the balancing
* endObject will be appended to this object. The
* endObject method must be called to mark the object's end.
*
* @return this
* @throws com.zabbix4j.utils.json.JSONException If the nesting is too deep, or if the object is
* started in the wrong place (for example as a key or after the end of the
* outermost array or object).
*/
public JSONWriter object() throws JSONException {
if (this.mode == 'i') {
this.mode = 'o';
}
if (this.mode == 'o' || this.mode == 'a') {
this.append("{");
this.push(new JSONObject());
this.comma = false;
return this;
}
throw new JSONException("Misplaced object.");
}
/**
* Pop an array or object scope.
*
* @param c The scope to close.
* @throws com.zabbix4j.utils.json.JSONException If nesting is wrong.
*/
private void pop(char c) throws JSONException {
if (this.top <= 0) {
throw new JSONException("Nesting error.");
}
char m = this.stack[this.top - 1] == null ? 'a' : 'k';
if (m != c) {
throw new JSONException("Nesting error.");
}
this.top -= 1;
this.mode = this.top == 0
? 'd'
: this.stack[this.top - 1] == null
? 'a'
: 'k';
}
/**
* Push an array or object scope.
*
* @param jo The scope to open.
* @throws com.zabbix4j.utils.json.JSONException If nesting is too deep.
*/
private void push(JSONObject jo) throws JSONException {
if (this.top >= maxdepth) {
throw new JSONException("Nesting too deep.");
}
this.stack[this.top] = jo;
this.mode = jo == null ? 'a' : 'k';
this.top += 1;
}
/**
* Append either the value true or the value
* false.
*
* @param b A boolean.
* @return this
* @throws com.zabbix4j.utils.json.JSONException
*/
public JSONWriter value(boolean b) throws JSONException {
return this.append(b ? "true" : "false");
}
/**
* Append a double value.
*
* @param d A double.
* @return this
* @throws com.zabbix4j.utils.json.JSONException If the number is not finite.
*/
public JSONWriter value(double d) throws JSONException {
return this.value(new Double(d));
}
/**
* Append a long value.
*
* @param l A long.
* @return this
* @throws com.zabbix4j.utils.json.JSONException
*/
public JSONWriter value(long l) throws JSONException {
return this.append(Long.toString(l));
}
/**
* Append an object value.
*
* @param object The object to append. It can be null, or a Boolean, Number,
* String, JSONObject, or JSONArray, or an object that implements JSONString.
* @return this
* @throws com.zabbix4j.utils.json.JSONException If the value is out of sequence.
*/
public JSONWriter value(Object object) throws JSONException {
return this.append(JSONObject.valueToString(object));
}
}
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