gson使用詳解

Gson.jar下載

JavaBean轉json

   //javaBean-->json
    @Test
    public void test1(){
        Gson gson = new Gson();
        Person p = new Person("張三", "123", 500, new Book("三國演義", "羅貫中"));
        String json = gson.toJson(p);
        System.out.println(json);
    }

json轉javabean

   //json-->javaBean
    @Test
    public void test2(){
        String json = "{\"username\":\"張三\",\"password\":\"123\",\"money\":500,\"book\":{\"id\":0,\"name\":\"三國演義\",\"price\":0,\"author\":\"羅貫中\"}}";
        Gson gson = new Gson();
        Person p = gson.fromJson(json, Person.class);
        System.out.println(p.getUsername()+"--"+p.getBook().getName());
    }

List集合轉json

  //list-->json
    @Test
    public void test3() {
        List<Person> list = new ArrayList<Person>();
        Person p = new Person("張三", "123", 500, new Book("三國演義", "羅貫中"));
        list.add(p);
        p = new Person("李四", "123", 500, new Book("三國演義", "羅貫中"));
        list.add(p);
        Gson gson = new Gson();
        String gsonStr = gson.toJson(list);
        System.out.println(gsonStr);
    }

Map集合轉json

 //map-->json
    @Test
    public void test4() {
        Map<String, Person> map = new HashMap<String, Person>();
        Person p = new Person("張三", "123", 500, new Book("三國演義", "羅貫中"));
        map.put("p1", p);
        p = new Person("李四", "123", 500, new Book("三國演義", "羅貫中"));
        map.put("p2", p);
        Gson gson = new Gson();
        String gsonStr = gson.toJson(map);
        System.out.println(gsonStr);
    }

json字符串轉List集合

 //json-->list
    @Test
    public void test5() {
        String str = "[{\"username\":\"張三\",\"password\":\"123\",\"money\":500,\"book\":{\"id\":0,\"name\":\"三國演義\",\"price\":0,\"author\":\"羅貫中\"}},{\"username\":\"李四\",\"password\":\"123\",\"money\":500,\"book\":{\"id\":0,\"name\":\"三國演義\",\"price\":0,\"author\":\"羅貫中\"}}]";
        Gson gson = new Gson();
        List<Person> ps = gson.fromJson(str,new TypeToken<List<Person>>() {

        }.getType());
        for (Person person : ps) {
            System.out.println(person.getUsername()+"---"+person.getBook().getName());
        }


}</pre><br />

json字符串轉Map集合 

  //json-->map
    @Test
    public void test6(){
        String str = "{\"p1\":{\"username\":\"張三\",\"password\":\"123\",\"money\":500,\"book\":{\"id\":0,\"name\":\"三國演義\",\"price\":0,\"author\":\"羅貫中\"}},\"p2\":{\"username\":\"李四\",\"password\":\"123\",\"money\":500,\"book\":{\"id\":0,\"name\":\"紅樓夢\",\"price\":0,\"author\":\"曹雪芹\"}}}";
        Gson gson = new Gson();
        Map<String, Person> map = gson.fromJson(str, new TypeToken<Map<String, Person>>(){}.getType());
        Set<String> keys = map.keySet();
        for(String key:keys){
            System.out.println(map.get(key).getUsername()+"--"+map.get(key).getBook().getName());
        }
    }


相關的兩個javabean 

Person.java 
public class Person {


private String username;
private String password;
private int money;
private Book book;

public Person() {
}

public Person(Book book) {
    this.book = book;
}

public Book getBook() {
    return book;
}
public void setBook(Book book) {
    this.book = book;
}
public String getUsername() {
    return username;
}
public void setUsername(String username) {
    this.username = username;
}
public String getPassword() {
    return password;
}
public void setPassword(String password) {
    this.password = password;
}
public int getMoney() {
    return money;
}
public void setMoney(int money) {
    this.money = money;
}

public Person(String username, String password, int money, Book book) {
    super();
    this.username = username;
    this.password = password;
    this.money = money;
    this.book = book;
}


}</pre>

Book.java 
public class Book {


private int id;
private String name;
private int price;
private String author;
private Detail detail;
private Attribute attribute;

public Attribute getAttribute() {
    return attribute;
}
public void setAttribute(Attribute attribute) {
    this.attribute = attribute;
}
public Detail getDetail() {
    return detail;
}
public void setDetail(Detail detail) {
    this.detail = detail;
}
public int getId() {
    return id;
}
public void setId(int id) {
    this.id = id;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public int getPrice() {
    return price;
}
public void setPrice(int price) {
    this.price = price;
}
public String getAuthor() {
    return author;
}
public void setAuthor(String author) {
    this.author = author;
}
public Book(String name, String author) {
    this.name = name;
    this.author = author;
}
public Book() {
}


}</pre>

注意事項： 

把json字符串轉為集合時，new TypeToken<>(){}.getType()在eclipse中貌似不能夠自動提示，如果你的電腦也是這樣的話，建議這里的代碼自己手動敲一下，eclipse只是不會自動提示，自己敲出來的是不會報錯的，嗯，我就遇到這一個小小的問題，總體來說這個東東還是很好用的。