昨天读一篇文章，看到gson这个词，一开始还以为作者写错了，问了度娘之后才发现是我才疏学浅，于是大概了解了一下gson用法，总体来说还是很简单的。

Gson.jar下载

JavaBean转json

//javaBean-->json
    @Test
    public void test1(){
        Gson gson = new Gson();
        Person p = new Person("张三", "123", 500, new Book("三国演义", "罗贯中"));
        String json = gson.toJson(p);
        System.out.println(json);
    }

json转javabean

//json-->javaBean
    @Test
    public void test2(){
        String json = "{\"username\":\"张三\",\"password\":\"123\",\"money\":500,\"book\":{\"id\":0,\"name\":\"三国演义\",\"price\":0,\"author\":\"罗贯中\"}}";
        Gson gson = new Gson();
        Person p = gson.fromJson(json, Person.class);
        System.out.println(p.getUsername()+"--"+p.getBook().getName());
    }

List集合转json

//list-->json
    @Test
    public void test3() {
        List<Person> list = new ArrayList<Person>();
        Person p = new Person("张三", "123", 500, new Book("三国演义", "罗贯中"));
        list.add(p);
        p = new Person("李四", "123", 500, new Book("三国演义", "罗贯中"));
        list.add(p);
        Gson gson = new Gson();
        String gsonStr = gson.toJson(list);
        System.out.println(gsonStr);
    }

Map集合转json

//map-->json
    @Test
    public void test4() {
        Map<String, Person> map = new HashMap<String, Person>();
        Person p = new Person("张三", "123", 500, new Book("三国演义", "罗贯中"));
        map.put("p1", p);
        p = new Person("李四", "123", 500, new Book("三国演义", "罗贯中"));
        map.put("p2", p);
        Gson gson = new Gson();
        String gsonStr = gson.toJson(map);
        System.out.println(gsonStr);
    }

json字符串转List集合

//json-->list
    @Test
    public void test5() {
        String str = "[{\"username\":\"张三\",\"password\":\"123\",\"money\":500,\"book\":{\"id\":0,\"name\":\"三国演义\",\"price\":0,\"author\":\"罗贯中\"}},{\"username\":\"李四\",\"password\":\"123\",\"money\":500,\"book\":{\"id\":0,\"name\":\"三国演义\",\"price\":0,\"author\":\"罗贯中\"}}]";
        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());
        }

    }

json字符串转Map集合

//json-->map
    @Test
    public void test6(){
        String str = "{\"p1\":{\"username\":\"张三\",\"password\":\"123\",\"money\":500,\"book\":{\"id\":0,\"name\":\"三国演义\",\"price\":0,\"author\":\"罗贯中\"}},\"p2\":{\"username\":\"李四\",\"password\":\"123\",\"money\":500,\"book\":{\"id\":0,\"name\":\"红楼梦\",\"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());
        }
    }

相关的两个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;
    }

}

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() {
    }

}

注意事项：

把json字符串转为集合时，​​new TypeToken<>(){}.getType()​​在eclipse中貌似不能够自动提示，如果你的电脑也是这样的话，建议这里的代码自己手动敲一下，eclipse只是不会自动提示，自己敲出来的是不会报错的，嗯，我就遇到这一个小小的问题，总体来说这个东东还是很好用的。