Java JSON组成和解析seo优化

Java JSON组成和解析

news/2024/10/2 16:28:35

　　本框架JSON元素组成和分析，JsonElement分三大类型JsonArray，JsonObject，JsonString。

　　JsonArray:数组和Collection子类，指定数组的话，使用ArrayList来add元素，遍历ArrayList再使用Array.newInstance生成数组并添加元素即可.

　　JsonObject:带有泛型的封装类，给带有泛型的字段赋值，关键在于如何根据“指定的类型”和“Field.getGenericType”来生成新的字段Type。

　　　　需要你了解java.lang.reflect.Type的子类

　　　　java.lang.reflect.GenericArrayType //通用数组类型 T[]
　　　　java.lang.reflect.ParameterizedType //参数类型,如: java.util.List<java.lang.String> java.util.Map<java.lang.String,java.lang.Object>
　　　　java.lang.reflect.TypeVariable //类型变量 K,V
　　　　java.lang.reflect.WildcardType //通配符类，例如： ?, ? extends Number, ? super Integer

　　　　java.lang.Class //int.class User.class .....

　　JsonString:分析字符串并解析成指定的对应类型

　　下面是本JSON框架的分析图

下面是简陋版的解析代码。该类没有解析日期，数值等代码，只是方便理解解析过程。

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);}/*** 当前指针指向的字符* @return*/public char current() {if(this.count==-1) return '\uffff';return this.cache[this.position];}/*** 当前指针指向的索引下标* @return*/public int position() {return this.position;}/*** 指针指向下一个字符，判断是否需要重新读取数据* @return* @throws IOException*/public boolean nextRead() throws IOException {return ++this.position>=this.count;}/*** 指针指向下一个字符* @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);}}/*** 跳过空白字符* @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;}/*** 关闭流* @throws IOException*/public void close() throws IOException{if(this.reader!=null){this.reader.close();this.reader = null;}}@Overridepublic char charAt(int index) {return this.cache[index];}@Overridepublic int length() {return this.count;}@Overridepublic 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;}@Overridepublic String toString() {if(this.count<0) return null;return new String(this.cache,this.position,this.count-this.position);}}