fastjson使用方法

Posted 2020-10-02

1.fastjson介绍

fastjson是一个Java语言编写的JSON处理器, 由阿里巴巴公司开发

2.测试用到的类Person.java 和 Role.java

public class Person {
	private String pname;
	
	// 对指定属性不转换json
	@JSONField(serialize=false)
	private Role role;
	
	public String getPname() {
		return pname;
	}
	public void setPname(String pname) {
		this.pname = pname;
	}
	public Role getRole() {
		return role;
	}
	public void setRole(Role role) {
		this.role = role;
	}
}

 

public class Role {
	private String rname;
	private Person person;
	
	public String getRname() {
		return rname;
	}
	public void setRname(String rname) {
		this.rname = rname;
	}
	public Person getPerson() {
		return person;
	}
	public void setPerson(Person person) {
		this.person = person;
	}
}

3.测试Demo

public class Demo1 {

	// 对象转json
	@Test
	public void run1() {
		Customer c = new Customer();
		c.setCust_id(20L);
		c.setCust_name("测试");
		c.setCust_phone("120");

		// 对象转为json
		String jsonString = JSON.toJSONString(c);
		// 打印结果 {"cust_id":20,"cust_name":"测试","cust_phone":"120"}
		System.out.println(jsonString);
	}

	// 集合转json
	@Test
	public void run2() {
		List<Customer> list = new ArrayList<Customer>();
		Customer c = new Customer();
		c.setCust_id(20L);
		c.setCust_name("测试");
		c.setCust_phone("120");
		Customer c2 = new Customer();
		c2.setCust_id(30L);
		c2.setCust_name("测试2");
		c2.setCust_phone("1200");

		list.add(c);
		list.add(c2);

		// 集合转为json
		String jsonString = JSON.toJSONString(list);
		// 打印结果
		// [{"cust_id":20,"cust_name":"测试","cust_phone":"120"},{"cust_id":30,"cust_name":"测试2","cust_phone":"1200"}]
		System.out.println(jsonString);
	}

	// fastjson禁止循环引用
	@Test
	public void run3() {
		List<Customer> list = new ArrayList<Customer>();
		Customer c = new Customer();
		c.setCust_id(20L);
		c.setCust_name("测试");
		c.setCust_phone("120");

		list.add(c);
		list.add(c);

		// 集合转为json
		String jsonString = JSON.toJSONString(list);
		// 打印结果
		// [{"cust_id":20,"cust_name":"测试","cust_phone":"120"},{"$ref":"$[0]"}]
		System.out.println(jsonString);

		// 集合转为json
		String jsonString1 = JSON.toJSONString(list, SerializerFeature.DisableCircularReferenceDetect);
		// 打印结果
		// [{"cust_id":20,"cust_name":"测试","cust_phone":"120"},{"cust_id":20,"cust_name":"测试","cust_phone":"120"}]
		System.out.println(jsonString1);
	}

	// fastjson禁止循环引用
	// Person和Role互相引用导致的死循环问题
	@Test
	public void run4() {
		Person p = new Person();
		p.setPname("小明");
		Role r = new Role();
		r.setRname("管理员");
		p.setRole(r);
		r.setPerson(p);

		String jsonString = JSON.toJSONString(p, SerializerFeature.DisableCircularReferenceDetect);
		// 打印结果 如果不加注解 StackOverflowError
		// 打印结果 如果加上注解@JSONField(serialize=false) {"pname":"小明"}
		System.out.println(jsonString);
	}

}

4.FastJsonUtils工具类

public class FastJsonUtil {

	/**
	 * 将对象转成json串
	 * @param object
	 * @return
	 */
	public static String toJSONString(Object object) {
		// DisableCircularReferenceDetect来禁止循环引用检测
		return JSON.toJSONString(object, SerializerFeature.DisableCircularReferenceDetect);
	}

	/*
	 * 输出json
	 */
	public static void write_json(HttpServletResponse response, String jsonString) {
		response.setContentType("application/json;utf-8");
		response.setCharacterEncoding("UTF-8");
		try {
			response.getWriter().print(jsonString);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	/**
	 * ajax提交后回调的json字符串
	 * @return
	 */
	public static String ajaxResult(boolean success, String message) {
		Map map = new HashMap();
		map.put("success", success);// 是否成功
		map.put("message", message);// 文本消息
		String json = JSON.toJSONString(map);
		return json;
	}

	/**
	 * JSON串自动加前缀
	 * @param json 原json字符串
	 * @param prefix 前缀
	 * @return 加前缀后的字符串
	 */
	public static String JsonFormatterAddPrefix(String json, String prefix, Map<String, Object> newmap) {
		if (newmap == null) {
			newmap = new HashMap();
		}
		Map<String, Object> map = (Map) JSON.parse(json);

		for (String key : map.keySet()) {
			Object object = map.get(key);
			if (isEntity(object)) {
				String jsonString = JSON.toJSONString(object);
				JsonFormatterAddPrefix(jsonString, prefix + key + ".", newmap);
			} else {
				newmap.put(prefix + key, object);
			}

		}
		return JSON.toJSONString(newmap);
	}

	/**
	 * 判断某对象是不是实体
	 * @param object
	 * @return
	 */
	private static boolean isEntity(Object object) {
		if (object instanceof String) {
			return false;
		}
		if (object instanceof Integer) {
			return false;
		}
		if (object instanceof Long) {
			return false;
		}
		if (object instanceof java.math.BigDecimal) {
			return false;
		}
		if (object instanceof Date) {
			return false;
		}
		if (object instanceof java.util.Collection) {
			return false;
		}
		return true;
	}
}