本框架JSON元素組成和分析，JsonElement分三大型別JsonArray，JsonObject，JsonString。
JsonArray:陣列和Collection子類，指定陣列的話，使用ArrayList來add元素，遍歷ArrayList再使用Array.newInstance生成陣列並新增元素即可.
JsonObject:帶有泛型的封裝類，給帶有泛型的欄位賦值，關鍵在於如何根據“指定的型別”和“Field.getGenericType”來生成新的欄位Type。
需要你瞭解java.lang.reflect.Type的子類
java.lang.reflect.GenericArrayType //通用陣列型別 T[]
java.lang.reflect.ParameterizedType //引數型別,如: java.util.List<java.lang.String> java.util.Map<java.lang.String,java.lang.Object>
java.lang.reflect.TypeVariable //型別變數 K,V
java.lang.reflect.WildcardType //萬用字元類，例如： ?, ? extends Number, ? super Integer
java.lang.Class //int.class User.class .....
JsonString:分析字串並解析成指定的對應型別
下面是本JSON框架的分析圖
下面是簡陋版的解析程式碼。該類沒有解析日期，數值等程式碼，只是方便理解解析過程。
package june.zero.json.reader; import java.io.IOException; import java.io.Reader; import java.io.StringReader; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; public class JsonSimpleParser implements CharSequence { public static void main(String[] args) { String json = "[{a:1,b:2},[1,2,3]]"; Object obj = new JsonSimpleParser().parse(json); System.out.println(obj); } protected static final String JSON_EXTRA_CHAR_ERROR = "Extra characters exist! "; protected static final String JSON_OBJECT_COLON_ERROR = "Wrong format of JsonObject, no separator colon! "; protected static final String JSON_OBJECT_END_ERROR = "The JsonObject format must end with comma as a separator or with right curly brace! "; protected static final String JSON_ARRAY_END_ERROR = "The JsonArray format must end with comma as a separator or with right bracket! "; protected static final String JSON_STRING2_END_ERROR = "The character starts with double quotation marks, but does not end with double quotation marks! "; protected static final String JSON_STRING1_END_ERROR = "The character starts with single quotation marks, but does not end with single quotation marks! "; protected Reader reader; protected static final int capacity = 1024; protected final char[] cache = new char[capacity]; protected int count; protected int position; public void read() throws IOException { this.position = 0; this.count = this.reader.read(this.cache,0,capacity); } /** * 當前指標指向的字元 * @return */ public char current() { if(this.count==-1) return '\uffff'; return this.cache[this.position]; } /** * 當前指標指向的索引下標 * @return */ public int position() { return this.position; } /** * 指標指向下一個字元，判斷是否需要重新讀取資料 * @return * @throws IOException */ public boolean nextRead() throws IOException { return ++this.position>=this.count; } /** * 指標指向下一個字元 * @return * @throws IOException */ public void next() throws IOException { if(++this.position>=this.count){ this.position = 0; this.count = this.reader.read(this.cache,0,capacity); } } /** * 跳過空白字元 * @throws IOException */ public void skip() throws IOException { while(this.count!=-1&&Character.isWhitespace(this.current())){ if(++this.position>=this.count){ this.position = 0; this.count = this.reader.read(this.cache,0,capacity); } } } public Object parse(String json) throws RuntimeException { return parse(new StringReader(json)); } /** * 解析 */ public Object parse(Reader reader) throws RuntimeException { try { this.reader = reader; this.read(); Object value = parse(); this.skip(); if(this.count!=-1){ throw new RuntimeException(JSON_EXTRA_CHAR_ERROR); } return value; } catch (Throwable e) { throw new RuntimeException(e); } finally { try { this.close(); } catch (IOException e) { } } } protected Object parse() throws IOException { this.skip(); char current = this.current(); if(current=='{'){ this.next(); this.skip(); Map<Object, Object> object = new HashMap<Object, Object>(); if(this.current() == '}') { this.next(); return object; } do{ Object key = parse(); this.skip(); if(this.current()!=':'){ throw new RuntimeException(JSON_OBJECT_COLON_ERROR); } this.next(); object.put(key, parse()); this.skip(); current = this.current(); if(current=='}') break; if(current!=','){ throw new RuntimeException(JSON_OBJECT_END_ERROR); } this.next(); this.skip(); }while(true); this.next(); return object; } if(current=='['){ this.next(); this.skip(); List<Object> array = new ArrayList<Object>(); if(this.current() == ']'){ this.next(); return array; } do{ array.add(parse()); this.skip(); current = this.current(); if(current==']') break; if(current!=','){ throw new RuntimeException(JSON_ARRAY_END_ERROR); } this.next(); this.skip(); }while(true); this.next(); return array; } this.skip(); StringBuilder string = new StringBuilder(); if(current=='"'){ this.next(); int offset = this.position; while(this.count!=-1&& this.current()!='"'){ if(this.nextRead()){ string.append(this, offset, this.position); offset = 0; this.position = 0; this.count = this.reader.read(this.cache,0,capacity); } } string.append(this, offset, this.position); if(this.current()!='"'){ throw new RuntimeException(JSON_STRING2_END_ERROR); } this.next(); return string; } if(current=='\''){ if(++this.position>=this.count){ this.position = 0; this.count = this.reader.read(this.cache,0,capacity); } int offset = this.position; while(this.count!=-1&&this.current()!='\''){ if(this.nextRead()){ string.append(this, offset, this.position); offset = 0; this.read(); } } string.append(this, offset, this.position); if(this.current()!='\''){ throw new RuntimeException(JSON_STRING1_END_ERROR); } this.next(); return string; } int offset = this.position; while(this.count!=-1&& (current = this.current())!=','&& current!=':'&& current!=']'&& current!='}'&& !Character.isWhitespace(current)){ if(this.nextRead()){ string.append(this, offset, this.position); offset = 0; this.read(); } } string.append(this, offset, this.position); return string; } /** * 關閉流 * @throws IOException */ public void close() throws IOException{ if(this.reader!=null){ this.reader.close(); this.reader = null; } } @Override public char charAt(int index) { return this.cache[index]; } @Override public int length() { return this.count; } @Override public CharSequence subSequence(int start, int end) { if (start < 0) throw new StringIndexOutOfBoundsException(start); if (end > count) throw new StringIndexOutOfBoundsException(end); if (start > end) throw new StringIndexOutOfBoundsException(end - start); StringBuilder string = new StringBuilder(); for (int i = start; i < end; i++) { string.append(this.cache[i]); } return string; } @Override public String toString() { if(this.count<0) return null; return new String(this.cache,this.position,this.count-this.position); } }
轉載請標明該來源。https://www.cnblogs.com/JuneZero/p/18252639
原始碼和jar包及其案例：https://www.cnblogs.com/JuneZero/p/18237283