Simple JSON開髮指南

Simple JSON是Google開發的Java JSON解析框架，基於Apache協議。

json-simple的主頁：//www.VeVB.COm/softs/455885.html

下載的文件是：json_simple.jar

例子1：很方便的方式，使用JSONValue

 System.out.println("=======decode======="); String s="[0,{/"1/":{/"2/":{/"3/":{/"4/":[5,{/"6/":7}]}}}}]"; Object obj=JSONValue.parse(s); JSONArray array=(JSONArray)obj; System.out.println("======the 2nd element of array======"); System.out.println(array.get(1)); System.out.println(); JSONObject obj2=(JSONObject)array.get(1); System.out.println("======field /"1/"=========="); System.out.println(obj2.get("1")); s="{}"; obj=JSONValue.parse(s); System.out.println(obj); s="[5,]"; obj=JSONValue.parse(s); System.out.println(obj); s="[5,,2]"; obj=JSONValue.parse(s); System.out.println(obj);

JSONObject是繼承Map的，而JSONArray是繼承List的，所以你可以用Map和List的標準方式來使用JSONObject和JSONArray。

而JSONValue則可以使用數組也可以用對象。

例子2：快速的方式，使用JSONParser

 JSONParser parser=new JSONParser(); System.out.println("=======decode======="); String s="[0,{/"1/":{/"2/":{/"3/":{/"4/":[5,{/"6/":7}]}}}}]"; Object obj=parser.parse(s); JSONArray array=(JSONArray)obj; System.out.println("======the 2nd element of array======"); System.out.println(array.get(1)); System.out.println(); JSONObject obj2=(JSONObject)array.get(1); System.out.println("======field /"1/"=========="); System.out.println(obj2.get("1")); s="{}"; obj=parser.parse(s); System.out.println(obj); s="[5,]"; obj=parser.parse(s); System.out.println(obj); s="[5,,2]"; obj=parser.parse(s); System.out.println(obj);

使用JSONParser需要捕獲異常。

例子3：異常處理

String jsonText = "[[null, 123.45, /"a//tb c/"]}, true"; JSONParser parser = new JSONParser(); try{ parser.parse(jsonText); } catch(ParseException pe){ System.out.println("position: " + pe.getPosition()); System.out.println(pe); }

執行結果：

 position:25 Unexpected token RIGHT BRACE(}) at position 25.

例子4：容器工廠

使用使用ContainerFactory類來創建一個容器工廠。

 String jsonText = "{/"first/": 123, /"second/": [4, 5, 6], /"third/": 789}"; JSONParser parser = new JSONParser(); ContainerFactory containerFactory = new ContainerFactory(){ public List creatArrayContainer() { return new LinkedList(); } public Map createObjectContainer() { return new LinkedHashMap(); } }; try{ Map json = (Map)parser.parse(jsonText, containerFactory); Iterator iter = json.entrySet().iterator(); System.out.println("==iterate result=="); while(iter.hasNext()){ Map.Entry entry = (Map.Entry)iter.next(); System.out.println(entry.getKey() + "=>" + entry.getValue()); } System.out.println("==toJSONString()=="); System.out.println(JSONValue.toJSONString(json)); } catch(ParseException pe){ System.out.println(pe); }

結果如下：

 ==iterate result== first=>123 second=>[4,5,6] third=>789 ==toJSONString()== {"first":123,"second":[4,5,6],"third":789}

 class KeyFinder implements ContentHandler{ private Object value; private boolean found = false; private boolean end = false; private String key; private String matchKey; public void setMatchKey(String matchKey){ this.matchKey = matchKey; } public Object getValue(){ return value; } public boolean isEnd(){ return end; } public void setFound(boolean found){ this.found = found; } public boolean isFound(){ return found; } public void startJSON() throws ParseException, IOException { found = false; end = false; } public void endJSON() throws ParseException, IOException { end = true; } public boolean primitive(Object value) throws ParseException, IOException { if(key != null){ if(key.equals(matchKey)){ found = true; this.value = value; key = null; return false; } } return true; } public boolean startArray() throws ParseException, IOException { return true; } public boolean startObject() throws ParseException, IOException { return true; } public boolean startObjectEntry(String key) throws ParseException, IOException { this.key = key; return true; } public boolean endArray() throws ParseException, IOException { return false; } public boolean endObject() throws ParseException, IOException { return true; } public boolean endObjectEntry() throws ParseException, IOException { return true; } }

 String jsonText ="{/"first/": 123, /"second/": [{/"k1/":{/"id/":/"id1/"}}, 4, 5, 6, {/"id/": 123}], /"third/": 789, /"id/": null}"; JSONParser parser =newJSONParser(); KeyFinder finder =newKeyFinder(); finder.setMatchKey("id"); try{ while(!finder.isEnd()){ parser.parse(jsonText, finder,true); if(finder.isFound()){ finder.setFound(false); System.out.println("found id:"); System.out.println(finder.getValue()); } } } catch(ParseException pe){ pe.printStackTrace(); }

 found id: id1 found id: 123 found id: null

class Transformer implements ContentHandler{ private Stack valueStack; public Object getResult(){ if(valueStack == null || valueStack.size() == 0) return null; return valueStack.peek(); } public boolean endArray () throws ParseException, IOException { trackBack(); return true; } public void endJSON () throws ParseException, IOException {} public boolean endObject () throws ParseException, IOException { trackBack(); return true; } public boolean endObjectEntry () throws ParseException, IOException { Object value = valueStack.pop(); Object key = valueStack.pop(); Map parent = (Map)valueStack.peek(); parent.put(key, value); return true; } private void trackBack(){ if(valueStack.size() > 1){ Object value = valueStack.pop(); Object prev = valueStack.peek(); if(prev instanceof String){ valueStack.push(value); } } } private void consumeValue(Object value){ if(valueStack.size() == 0) valueStack.push(value); else{ Object prev = valueStack.peek(); if(prev instanceof List){ List array = (List)prev; array.add(value); } else{ valueStack.push(value); } } } public boolean primitive (Object value) throws ParseException, IOException { consumeValue(value); return true; } public boolean startArray () throws ParseException, IOException { List array = new JSONArray(); consumeValue(array); valueStack.push(array); return true; } public void startJSON () throws ParseException, IOException { valueStack = new Stack(); } public boolean startObject () throws ParseException, IOException { Map object = new JSONObject(); consumeValue(object); valueStack.push(object); return true; } public boolean startObjectEntry (String key) throws ParseException, IOException { valueStack.push(key); return true; } }

 String jsonString = <Input JSON text>; Object value = null; JSONParser parser = new JSONParser(); Transformer transformer = new Transformer(); parser.parse(jsonString, transformer); value = transformer.getResult();

 String jsonString =<Input JSON text>; Object value =null; JSONParser parser =newJSONParser(); value = parser.parse(jsonString);

json_encode ― 對變量進行JSON 編碼。

說明：string json_encode ($value )，返回value 值的JSON 形式。

參數：待編碼的value ，除了resource 類型之外，可以為任何數據類型

該函數只能接受UTF-8 編碼的數據（譯註：指字符/字符串類型的數據）

返回值：編碼成功則返回一個以JSON 形式表示的string 。