+1 for JohnS's gson answer, but here's a way with the "standard" JSONObject library:
public class JsonFormatter{
public static String format(final JSONObject object) throws JSONException{
final JsonVisitor visitor = new JsonVisitor(4, ' ');
visitor.visit(object, 0);
return visitor.toString();
}
private static class JsonVisitor{
private final StringBuilder builder = new StringBuilder();
private final int indentationSize;
private final char indentationChar;
public JsonVisitor(final int indentationSize, final char indentationChar){
this.indentationSize = indentationSize;
this.indentationChar = indentationChar;
}
private void visit(final JSONArray array, final int indent) throws JSONException{
final int length = array.length();
if(length == 0){
write("[]", indent);
} else{
write("[", indent);
for(int i = 0; i < length; i++){
visit(array.get(i), indent + 1);
}
write("]", indent);
}
}
private void visit(final JSONObject obj, final int indent) throws JSONException{
final int length = obj.length();
if(length == 0){
write("{}", indent);
} else{
write("{", indent);
final Iterator<String> keys = obj.keys();
while(keys.hasNext()){
final String key = keys.next();
write(key + " :", indent + 1);
visit(obj.get(key), indent + 1);
if(keys.hasNext()){
write(",", indent + 1);
}
}
write("}", indent);
}
}
private void visit(final Object object, final int indent) throws JSONException{
if(object instanceof JSONArray){
visit((JSONArray) object, indent);
} else if(object instanceof JSONObject){
visit((JSONObject) object, indent);
} else{
if(object instanceof String){
write("\"" + (String) object + "\"", indent);
} else{
write(String.valueOf(object), indent);
}
}
}
private void write(final String data, final int indent){
for(int i = 0; i < (indent * indentationSize); i++){
builder.append(indentationChar);
}
builder.append(data).append('\n');
}
@Override
public String toString(){
return builder.toString();
}
}
}
Usage:
public static void main(final String[] args) throws JSONException{
final JSONObject obj =
new JSONObject("{\"glossary\":{\"title\": \"example glossary\", \"GlossDiv\":{\"title\": \"S\", \"GlossList\":{\"GlossEntry\":{\"ID\": \"SGML\", \"SortAs\": \"SGML\", \"GlossTerm\": \"Standard Generalized Markup Language\", \"Acronym\": \"SGML\", \"Abbrev\": \"ISO 8879:1986\", \"GlossDef\":{\"para\": \"A meta-markup language, used to create markup languages such as DocBook.\", \"GlossSeeAlso\": [\"GML\", \"XML\"]}, \"GlossSee\": \"markup\"}}}}}");
System.out.println(JsonFormatter.format(obj));
}
Output:
{
glossary :
{
title :
"example glossary"
,
GlossDiv :
{
GlossList :
{
GlossEntry :
{
SortAs :
"SGML"
,
GlossDef :
{
GlossSeeAlso :
[
"GML"
"XML"
]
,
para :
"A meta-markup language, used to create markup languages such as DocBook."
}
,
GlossSee :
"markup"
,
GlossTerm :
"Standard Generalized Markup Language"
,
ID :
"SGML"
,
Acronym :
"SGML"
,
Abbrev :
"ISO 8879:1986"
}
}
,
title :
"S"
}
}
}
