springboot返回json

public class Demo {
    private int id;
    private String name;

    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 class JsonStringController{
    @RequestMapping("/hello")
    public String hello(){
        return "hello";
    }
    @RequestMapping("/jsonString")
    public Demo getDemo(){
        Demo demo=new Demo();
        demo.setId(1);
        demo.setName("我是json字符串");
        return demo;
    }
}