Gson在Java中的簡要使用

最近在把一個數組或字符串轉化成對象時，使用了Google的Gson感覺不錯，下面我以代碼的形式詳細舉例來介紹

上面的注釋部分為輸出結果，使用了maven ，這裡是Gson的maven依賴

<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.2</version>
</dependency>

package gson;

import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.junit.Test;

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

public class AllInAllGSON {
Gson gson = new Gson();//生成一個json對象
@Test
/**
* [1,2,3,4,5,6,7,8,9,0] ["one","two","three","four","five","six","seven","eight","nine","zero"] [[1,2,3],[3,4,5],[4,5,6]]
* 3 1n3 2n3 3n3 4n3 5n3 6n3 7n3 8n3 9n3 0n4 onen4 twon4 threen4 fourn4 fiven4 sixn4 sevenn4 eightn4 ninen4 zero data 1 data 2 data 3
*data 3 data 4 data 5
data 4 data 5 data 6
*/
public void arrayToJson(){
int [] n1 = {1,2,3,4,5,6,7,8,9,0};
int[][] data = {{1, 2, 3}, {3, 4, 5}, {4, 5, 6}};
String [] n2 = {"one","two","three","four","five","six","seven","eight","nine","zero"};

String x1 = gson.toJson(n1);//把數組轉化成json
String x2 = gson.toJson(n2);
String x3 = gson.toJson(data);
System.out.println(x1+ " "+ x2+" "+x3);
int [] n3 = gson.fromJson(x1, int[].class);//把一個json轉成數組
String [] n4 = gson.fromJson(x2, String[].class);
int [][] n5 = gson.fromJson(x3, int[][].class);
for(int i=0;i<n3.length;i++){
System.out.print("n3 "+n3[i]);
}
for(int i=0;i<n4.length;i++){
System.out.print("n4 "+n4[i]);
}
for(int i=0;i<data.length;i++){
for(int j=0;j<data[i].length;j++){
System.out.print(" data "+data[i][j]);
}
System.out.println("");
}
}
@Test
/**
* list ["hi","hello","how"]
* [{"name":"Alice","address":"AppSt","dateOfBirth":"Nov 1, 3900 12:00:00 AM"},{"name":"Bob","address":"Baa St"},{"name":"Carol","address":"Grape St","dateOfBirth":"Jun 21, 3900 12:00:00 AM"},{"name":"Mallory","address":"Mango St"}]
name Alice
name Bob
name Carol
name Mallory
*/
public void listToJson(){
List<String> list = new ArrayList<String>();//把一個list集合轉化成json串
list.add("hi");
list.add("hello");
list.add("how");
String str = gson.toJson(list);
System.out.println("list "+str);
Student a = new Student("Alice", "AppSt", new Date(2000, 10, 1));
Student b = new Student("Bob", "Baa St", null);
Student c = new Student("Carol", "Grape St", new Date(2000, 5, 21));
Student d = new Student("Mallory", "Mango St", null);
List<Student> student = new ArrayList<Student>();
student.add(a);
student.add(b);
student.add(c);
student.add(d);
String str1 = gson.toJson(student);
System.out.println(str1);
Type type = new TypeToken<List<Student>>(){}.getType();//把json串轉化成一個student對象
List<Student> stu = gson.fromJson(str1, type);
for(Student s:stu){
System.out.println("name " + s.getName());
}
}
@Test
/**
* {"WHITE":"5454#FFFFFF","BLUE":"0000FF","YELLOW":"sd#FFFF00","GREEN":"1008000","BLACK":"000000","RED":"#FeF0000"}
map 5454#FFFFFF
map 0000FF
map sd#FFFF00
map 1008000
map 000000
map #FeF0000
*/
public void mapToJson(){
Map<String, String> colours = new HashMap<String, String>();
colours.put("BLACK", "000000");
colours.put("RED", "#FeF0000");
colours.put("GREEN", "1008000");
colours.put("BLUE", "0000FF");
colours.put("YELLOW", "sd#FFFF00");
colours.put("WHITE", "5454#FFFFFF");
String str = gson.toJson(colours);
System.out.println(str);
Type type = new TypeToken<Map<String,String>>() {}.getType();
Map<String,String> map = gson.fromJson(str, type);
for(String key:map.keySet()){
System.out.println("map " + map.get(key));
}
}
@Test
/**
* {"name":"Bob","address":"Baa St"}
Bob
*/
public void stuClass(){
Student b = new Student("Bob", "Baa St", null);//對一個類的屬性進行轉成json串
String str = gson.toJson(b);
System.out.println(str);
Student stu = gson.fromJson(str, Student.class);//把json轉成java對象
System.out.println(stu.getName());
}
}

Student類

package gson;
import java.util.Date;

public class Student {
private String name;
private String address;
private Date dateOfBirth;

public Student() {
}

public Student(String name, String address, Date dateOfBirth) {
this.name = name;
this.address = address;
this.dateOfBirth = dateOfBirth;
}

public String getName() {
return name;
}

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

public String getAddress() {
return address;
}

public void setAddress(String address) {
this.address = address;
}

public Date getDateOfBirth() {
return dateOfBirth;
}

public void setDateOfBirth(Date dateOfBirth) {
this.dateOfBirth = dateOfBirth;
}
}

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