Gson在解析java数据格式的三种范例

       Gson是谷歌提供的一个开源库，用来解析json格式的数据非常好用。如果用maven进行项目管理的话，可以在pom.xml中引入如下依赖：
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.0</version>
</dependency>      如果不是，请自行下载jar包：gson-2.8.0.jar。
   接下来讲述如何用Gson进行单条无嵌套Json数据的解析、单条有嵌套的json数据解析和解析json数组：
import com.google.gson.Gson;

public class GJsonExap {
public static void main(String[] args) {
/*
一、单条无嵌套json数据的解析
*/
//给出如下的json，将如下json数据解析成Person对象

String gStr = "{'name':'Json','age':20}";
String gStr1 = "{\"name\":\"Rose\",\"age\":12}";
Gson gson = new Gson();
Person person = gson.fromJson(gStr,Person.class);
Person person1 = gson.fromJson(gStr1,Person.class);
System.out.println(person.toString());
System.out.println(person1.toString());
}
}
class Person{
private String name;
private int age;

public Person() {
}

public Person(String name, int age) {
this.name = name;
this.age = age;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}

@Override
public String toString() {
return "Person{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
import com.google.gson.Gson;

public class GsonTest1{
/*
考虑到json数据的不同，那么解析Json时候所用的类也可能不同，比如这里
你可能用Person，而如果解析其他数据时又变成Dog.Cat了，因此考虑
将Gson解析的步骤封装，并提供泛型参数，示例如下

*/
public static void main(String[] args) {
String strJson = "{\"name\":\"wangcai\",\"category\":\"旺旺\"}";
Dog dog = parseJsonWithGson(strJson,Dog.class);
System.out.println(dog.toString());
}
public static <T> T parseJsonWithGson(String jsonData,Class<T>type){
Gson gson = new Gson();
return gson.fromJson(jsonData,type);
}
}
class Dog{
private String name;
private String category;

public Dog() {
}

public Dog(String name, String category) {
this.name = name;
this.category = category;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getCategory() {
return category;
}

public void setCategory(String category) {
this.category = category;
}

@Override
public String toString() {
return "Dog{" +
"name='" + name + '\'' +
", category='" + category + '\'' +
'}';
}
}

package cn.itcast.scala.generic.java;

public class GsonTest2 {
/*
二、单条有嵌套的json数据：{"name":"John","age":"20","grade":{"course":"English","score":"100","level":"A"}}
此类数据要用公共内部类来解决
*/
public static void main(String[] args) {
String strJson = "{\"name\":\"John\",\"age\":20,\"grade\":{\"course\":\"English\",\"score\":100,\"Level\":\"A\"}}";
String strJson1 = "{'name':'Rose','age':22,'grade':{'course':'English','score':100,'level':'A'}}";
//用先前GsonTest1中封装的Gson解析工具类，提供泛型参数
Student stu1 = GsonTest1.parseJsonWithGson(strJson,Student.class);
Student stu2 = GsonTest1.parseJsonWithGson(strJson1,Student.class);
System.out.println(stu1.toString());
System.out.println(stu2.toString());
}
}
// 一、根据Json数据串定义Student对象
class Student{
private String name;
private int age;
private Grade grade;
public class Grade{
private String course;
private int score;
private String level;

public String getCourse() {
return course;
}

public void setCourse(String course) {
this.course = course;
}

public int getScore() {
return score;
}

public void setScore(int score) {
this.score = score;
}

public String getLevel() {
return level;
}

public void setLevel(String level) {
this.level = level;
}

@Override
public String toString() {
return "Grade{" +
"course='" + course + '\'' +
", score=" + score +
", level='" + level + '\'' +
'}';
}
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}

public Grade getGrade() {
return grade;
}

public void setGrade(Grade grade) {
this.grade = grade;
}

@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
", grade=" + grade +
'}';
}
}

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
package cn.itcast.scala.generic.java;

import java.util.List;

public class GsonTest3 {
/*
三、 解析Json数组：比如有如下Json数据：json数组最外层要加“[]”
[{'name':'John','grade':[{'course':'English','score':100},{'course':'Math','score':78}]},
{'name':'Tom','grade':[{'course':'English','score':90},{'course':'Math','score':87}]}]
Student(name,grade[English,Math])
处理这类数据要用到List
*/
public static void main(String[] args) {

String jsonDate = "[{'name':'John', 'grade':[{'course':'English','score':100},{'course':'Math','score':78}]},{'name':'Tom', 'grade':[{'course':'English','score':86},{'course':'Math','score':90}]}]";

List<Stu> students =GsonUtil.parsJsonArrayWithGson(jsonDate,Stu.class);
System.out.println(students);
}
}

//下面是我重新写的一个Json工具类

package cn.itcast.scala.generic.java;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

import java.util.List;

public class GsonUtil {
//将json对象解析成相应的映射对象
public static <T> T parseJsonWithGson(String str,Class<T> type){
Gson gson = new Gson();
return gson.fromJson(str,type);
}
//将json对象解析成相应的映射对象列表
public static <T> List<T> parsJsonArrayWithGson(String str,Class<T> type){
Gson gson  = new Gson();
/*GSON提供了 TypeToken 这个类来帮助我们捕获（capture）像List<MyZhuiHaoDetailModel>这样的泛型信息。
上文创建了一个匿名内部类，这样，Java编译器就会把泛型信息编译到这个匿名内部类里，然后在运行时就可以被
getType()方法用反射API提取到。
*/
return gson.fromJson(str,new TypeToken<List<T>>(){
}.getType());
}
}

class Stu{ private String name; private List<Grade> grade; public class Grade{ private String course; private int score; public String getCourse() { return course; } public void setCourse(String course) { this.course = course; } public int getScore() { return score; } public void setScore(int score) { this.score = score; } @Override public String toString() { return "Grade{" + "course='" + course + '\'' + ", score=" + score + '}'; } } public String getName() { return name; } public void setName(String name) { this.name = name; } public List<Grade> getGrade() { return grade; } public void setGrade(List<Grade> grade) { this.grade = grade; } @Override public String toString() { return "Student{" + "name='" + name + '\'' + ", grade=" + grade + '}'; }}