The source code to reproduce https://github.com/alibaba/fastjson/issues/1422

FastJson37Issue.java

package testapp;

import com.alibaba.fastjson.JSON;

public class FastJson37Issue {

    public static class Foo {
        private boolean v;
        public void setV(boolean v) {
            this.v = v;
        }

        @Override
        public String toString() {
            return String.valueOf(v);
        }
    }

    public static void main(String[] args) {
        String fastJsonVersion = JSON.VERSION;
        System.out.println("fastjson version: " + fastJsonVersion);

        String strOk = "{\"v\": 111}";
        Foo ok = JSON.parseObject(strOk, Foo.class);
        System.out.println("ok:" + ok);

        String strBad = "{\"v\":111}";
        Foo bad = JSON.parseObject(strBad, Foo.class);
        System.out.println("bad" + bad);
    }

}