java怎么使用gson解析json字符串

Gson是谷歌推出的解析json数据以及将对象转换成json数据的一个开源框架. 现在json因其易读性和高效率而被广泛的使用着. 

相对于java以及其它json的解析框架,Gson非常的好用.

简单来讲就是根据json的数据结构定义出相应的javabean --->"new"出Gson的实例gson---->gson.fromJson(jsonString,JavaBean.class) 即可.

下面给出一个实例来说明.

步骤1:目标:将从webservice传回的json

{
    "status": 0,
    "result": {
        "location": {
            "lng": 103.98964143811,
            "lat": 30.586643130352
        },
        "formatted_address": "四川省成都市双流县北一街154",
        "business": "簇桥,金花桥",
        "addressComponent": {
            "city": "成都市",
            "district": "双流县",
            "province": "四川省",
            "street": "北一街",
            "street_number": "154"
        },
        "cityCode": 75
    }
}

先普及下json数据格式定义: json数据只有两种格式.

一种是对象: 一个大括号包裹的内容就是一个对象.里面是无数个逗号相间隔的键值对

{ "firstName": "Brett", "lastName":"McLaughlin", "email": "aaaa" }

一种是数组:一个方括号包裹的内容就是一个数组,里面是无数个逗号相间隔的json对象

如:

{
    "people": [
        {
            "firstName": "Brett",
            "lastName": "McLaughlin",
            "email": "aaaa"
        },
        {
            "firstName": "Jason",
            "lastName": "Hunter",
            "email": "bbbb"
        },
        {
            "firstName": "Elliotte",
            "lastName": "Harold",
            "email": "cccc"
        }
    ]
}

步骤2 定义json数据格式对应的javaBean

public class Result {
private Integerstatus;
private ResultDetailresult;
public Result() {
}
public Result(Integer status, ResultDetail result) {
super();
this.status = status;
this.result = result;
}
public ResultDetail getResult() {
return this.result;
}
public Integer getStatus() {
return this.status;
}
public void setResult( ResultDetail result ) {
this.result = result;
}
public void setStatus( Integer status ) {
this.status = status;
}
@Override
public String toString() {
return "Result [status=" + this.status + ", result=" + this.result
+ "]";
}
}
public class ResultDetail {
Locationlocation;
Stringformatted_address;
AddressComponentaddressComponent;
Stringbusiness;
StringcityCode;
public ResultDetail() {
super();
// TODO Auto-generated constructor stub
}
public ResultDetail(Location location, String formatted_address,
AddressComponent addressComponent, String business, String cityCode) {
super();
this.location = location;
this.formatted_address = formatted_address;
this.addressComponent = addressComponent;
this.business = business;
this.cityCode = cityCode;
}
public AddressComponent getAddressComponent() {
return this.addressComponent;
}
public String getBusiness() {
return this.business;
}
public String getCityCode() {
return this.cityCode;
}
public String getFormatted_address() {
return this.formatted_address;
}
public Location getLocation() {
return this.location;
}
public void setAddressComponent( AddressComponent addressComponent ) {
this.addressComponent = addressComponent;
}
public void setBusiness( String business ) {
this.business = business;
}
public void setCityCode( String cityCode ) {
this.cityCode = cityCode;
}
public void setFormatted_address( String formatted_address ) {
this.formatted_address = formatted_address;
}
public void setLocation( Location location ) {
this.location = location;
}
}
public class Location {
Stringlng;
Stringlat;
public Location() {
}
public Location(String lng, String lat) {
this.lng = lng;
this.lat = lat;
}
public String getLat() {
return this.lat;
}
public String getLng() {
return this.lng;
}
public void setLat( String lat ) {
this.lat = lat;
}
public void setLng( String lng ) {
this.lng = lng;
}
@Override
public String toString() {
return "Location [lng=" + this.lng + ", lat=" + this.lat + "]";
}
}
public class AddressComponent {
Stringcity;
Stringdistrict;
Stringprovince;
Stringstreet;
Stringstreet_number;
public AddressComponent() {
super();
// TODO Auto-generated constructor stub
}
public AddressComponent(String city, String district, String province,
String street, String street_number) {
super();
this.city = city;
this.district = district;
this.province = province;
this.street = street;
this.street_number = street_number;
}
public String getCity() {
return this.city;
}
public String getDistrict() {
return this.district;
}
public String getProvince() {
return this.province;
}
public String getStreet() {
return this.street;
}
public String getStreet_number() {
return this.street_number;
}
public void setCity( String city ) {
this.city = city;
}
public void setDistrict( String district ) {
this.district = district;
}
public void setProvince( String province ) {
this.province = province;
}
public void setStreet( String street ) {
this.street = street;
}
public void setStreet_number( String street_number ) {
this.street_number = street_number;
}
@Override
public String toString() {
return "AddressComponent [city=" + this.city + ", district="
+ this.district + ", province=" + this.province + ", street="
+ this.street + ", street_number=" + this.street_number + "]";
}
}

测试:

jsonString ( 目标json数据,已经在最上面写好的)

System.out.println( "jsonString:" + jsonString );
Gson gson = new Gson();
Result fromJson = gson.fromJson( jsonString.toString() ,Result.class );
System.out.println( "******************************************" );
System.out.println( fromJson );

结果:

jsonString:{"status":0,"result":{"location":{"lng":103.98964143811,"lat":30.586643130352},"formatted_address":"四川省成都市双流县北一街154","business":"簇桥,金花桥","addressComponent":{"city":"成都市","district":"双流县","province":"四川省","street":"北一街","street_number":"154"},"cityCode":75}}
*******************************************
Result [status=0, result=ResultDetail [location=Location [lng=103.98964143811, lat=30.586643130352], formatted_address=四川省成都市双流县北一街154, addressComponent=AddressComponent [city=成都市, district=双流县, province=四川省, street=北一街, street_number=154], business=簇桥,金花桥, cityCode=75]]

可见,jsonString已经成功的被转换成了对应的javaBean

步骤3 : 总结.说明

Gson可以很轻松的实现javaBean和jsonString之间的互转.只需要明白json如何定义.剩下的就非常简单了.