Gson的JsonWriter和JsonReader代码详解例子
package com.app.json;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStream;import java.io.OutputStreamWriter;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import com.app.entity.duapp.Address;import com.google.gson.Gson;import com.google.gson.reflect.TypeToken;import com.google.gson.stream.JsonReader;import com.google.gson.stream.JsonWriter;/** * @date:2013-07-21 * @author ljl * */@SuppressWarnings("all")public class JsonWriterReader {private static Gson gson = new Gson();public static void main(String[] args) throws Exception {List<Map<String, String>> list = new ArrayList<Map<String, String>>();Map map1 = new HashMap();map1.put("country", "中国");map1.put("province", "广东省");map1.put("city", "广州市");map1.put("district", "天河区");map1.put("street", "棠东");Map map2 = new HashMap();map2.put("country", "中国");map2.put("province", "广东省");map2.put("city", "广州市");map2.put("district", "越秀区");map2.put("street", "五羊新邨");list.add(map1);list.add(map2);String[] str = new String[2];str[0]="中国";str[1]="美国"; Address add = new Address(1, "中国");List<Map> mapList = printlnJsonInfo(list, map1, str, add);/**写*/File file = writerJsonToFile(gson, mapList);/***读*/readJsonFromFile(gson, file);}/** * 打印Json信息 * @param list * @param map1 * @param str * @param add * @return */private static List<Map> printlnJsonInfo(List<Map<String, String>> list, Map map1,String[] str, Address add) {String listsJson = gson.toJson(list);// 集合转jsonString mapJson = gson.toJson(map1);// map转jsonString arrayJson = gson.toJson(str);// 数组转jsonString ObjJson = gson.toJson(add);// 对象转jsonSystem.out.println("->********************Object to JSON********************->");System.out.println("list -> 转Json: " + listsJson);System.out.println("Map对象 -> 转Json: " + mapJson);System.out.println("String数组 -> 转Json: " + arrayJson);System.out.println("Object -> 转Json: " + ObjJson);System.out.println("->********************JSON to Object ********************->");List<Address> listUser = new ArrayList<Address>();//从str遍历添加了多个对象for (int i = 0; i<str.length; i++) {listUser.add(new Address(i,str[i]));}String listJson = gson.toJson(listUser);System.out.println("Json-> 转泛型集合: " + listJson);List<Address> listAdd = gson.fromJson(listJson,new TypeToken<List<Address>>() {}.getType());for (Address addr : listAdd) {System.out.println("国家：" + addr.getCountry());}System.out.println("Json -> 转泛型集合List<Map<String,String>>: " + listsJson);List<Map> mapList = gson.fromJson(listsJson,new TypeToken<List<Map<String, String>>>() {}.getType());for (Map map : mapList) {System.out.println("地区:" + map.get("street"));}System.out.println("Json -> 转Oject: " + listsJson);Address ad = gson.fromJson(ObjJson, Address.class);System.out.println("国家:"+ad.getCountry());return mapList;}/** * JsonWriter * 把Json数据写入文件里面 * @param gson * @param mapList * @return * @throws Exception */private static File writerJsonToFile(Gson gson, List<Map> mapList)throws Exception {File file = new File("gson");// 把json保存项目根目录下无后缀格式的文本OutputStream out = new FileOutputStream(file);JsonWriter writer = new JsonWriter(new OutputStreamWriter(out, "UTF-8"));//设计编码gson.toJson(mapList, new TypeToken<List<Map<String, String>>>() {}.getType(), writer);writer.flush();writer.close();return file;}/** * JsonReader * 读取从本地文件的Json数据 * @param gson * @param file * @throws Exception */private static void readJsonFromFile(Gson gson, File file)throws Exception {InputStream input = new FileInputStream(file);JsonReader reader = new JsonReader(new InputStreamReader(input));List<Map> content = gson.fromJson(reader,new TypeToken<List<Map<String, String>>>() {}.getType());//List<Map> content = gson.fromJson(new InputStreamReader(input),new TypeToken<List<Map<String, String>>>() {}.getType());for (Map map : content) {System.out.println("地区:" + map.get("street"));}reader.close();}}
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[{"street":"棠东","province":"广东省","district":"天河区","city":"广州市","country":"中国"},{"street":"五羊新邨","province":"广东省","district":"越秀区","city":"广州市","country":"中国"}]?
package com.app.entity.duapp;import java.io.Serializable;import com.google.gson.annotations.Expose;/** * Gson gson=new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create(); * 创建Gson对象,没有@Expose注释的属性将不会被序列化 * serialize序列化 默认 true * deserialize反序列化 默认 true */public class Address implements Serializable{@Expose(serialize=false)// 序列化 /Address类已经序列化private int id;@Expose(deserialize=false)// 反序列化private String country;//国家private String province;//省份private String city;//城市private String street;//街道private String district;//地区private String cityCode;//邮政编码private String streetNumber;//街道号public Address() {}public Address(int id,String country) {this.id=id;this.country=country;}public String getCityCode() {return cityCode;}public void setCityCode(String cityCode) {this.cityCode = cityCode;}public String getStreetNumber() {return streetNumber;}public void setStreetNumber(String streetNumber) {this.streetNumber = streetNumber;}public String getStreet() {return street;}public void setStreet(String street) {this.street = street;}public String getDistrict() {return district;}public void setDistrict(String district) {this.district = district;}public String getCity() {return city;}public void setCity(String city) {this.city = city;}public String getProvince() {return province;}public void setProvince(String province) {this.province = province;}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getCountry() {return country;}public void setCountry(String country) {this.country = country;}}?