前言
额，json的介绍就不多说了，非常方便。对于json相关的处理也是工作中非常基础的一部分。不过之前非常乱，最近搜了搜资料，对fastjson做了一个总结，相信以后的json格式上应该是没什么问题了。
主要内容
概括
先概括一下主要的知识点，理一理思绪，对下一步的学习还是十分关键的。
1.测试中我们会接触到三种对象，分别的JSON对象，json串，javabean。JSON对象就是JSONObject，fastjson框架中提供的json对象，剩下2个就不说了。
2.测试的对象主要包括：简单json，复杂json，json数组
显而易见，我们测试的内容就是分别针对（简单json，复杂json，json数组）做（JSON对象，json串，javabean）的两两转换。
简单json
先放上简单json的测试数据：
//javabean,省略构造方法，set，get等
public class Simple implements Serializable {
private String name;
private String sex;
private Integer age;
}
static {
simpleBean = new Simple();
simpleBean.setAge(15);
simpleBean.setName("fff");
simpleBean.setSex("male");
}
//json串
public static String simpleJson = "{\"name\": \"ttt\",\"age\": 12,\"sex\": \"male\"}";
JSON <==> json串
//JSON=>json
JSONObject jsonObject = JSONObject.parseObject(simpleJson);
String json = jsonObject.toJSONString();
System.out.println(json);//{"sex":"male","name":"ttt","age":12}
//JSON<=json
JSONObject jsonObject = JSONObject.parseObject(simpleJson);
System.out.println(jsonObject.get("sex"));//male
JSON <==> javabean
//JSON=>javabean
JSONObject jsonObject2 = JSONObject.parseObject(complexJson);
Simple simple1 = JSONObject.parseObject(jsonObject1.toJSONString(), new TypeReference<Simple>() {});
System.out.println(simple1);//Simple{name='ttt', sex='male', age=12}
//JSON<=javabean
JSONObject jsonObject = JSONObject.parseObject(JSONObject.toJSONString(simpleBean));
System.out.println(jsonObject.get("name"));
Json串 <==> javabean
//json串=>javabean
Simple simple = JSONObject.parseObject(simpleJson, Simple.class);
System.out.println(simple);//Simple{name='ttt', sex='male', age=12}
Simple simple1 = JSONObject.parseObject(simpleJson, new TypeReference<Simple>() {});
System.out.println(simple1);//Simple{name='ttt', sex='male', age=12}
//json串<=javabean
String jsonString = JSON.toJSONString(simpleBean);
System.out.println(jsonString);//{"age":15,"name":"fff","sex":"male"}
复杂json
测试数据：
//javabean
public class Complex {
private Integer index;
private List<Simple> simples;
private List<Integer> grades;
}
static {
complexBean = new Complex();
complexBean.setGrades(Arrays.asList(1, 2, 4, 5, 6));
complexBean.setIndex(1);
complexBean.setSimples(Arrays.asList(new Simple("ggg", "male", 17)
, new Simple("ttt", "male", 18)
, new Simple("yyy", "male", 19)
));
}
//json串
public static String complexJson = "{\"simples\":[{\"name\": \"ttt\",\"age\": 12,\"sex\": \"male\"},{\"name\": \"fff\",\"age\": 13,\"sex\": \"female\"}],\"index\":5,\"grades\":[12,32,43,51]}";
JSON <==> json串
//JSON=>json
JSONObject jsonObject = JSONObject.parseObject(complexJson);
String json = jsonObject.toJSONString();
System.out.println(json);
//JSON<=json
JSONObject jsonObject = JSONObject.parseObject(complexJson);
System.out.println(jsonObject.get("grades"));//[12,32,43,51]
System.out.println(jsonObject.toString());//{"index":5,"grades":[12,32,43,51],"simples":[{"sex":"male","name":"ttt","age":12},{"sex":"female","name":"fff","age":13}]}
if (jsonObject.get("simples") != null) {
System.out.println(JSONObject.parseObject(JSONArray.parseArray(jsonObject.get("simples").toString()).get(1).toString()).get("sex"));//female
}
JSON <==> javabean
//JSON=>javabean
JSONObject jsonObject2 = JSONObject.parseObject(complexJson);
Complex complex1 = JSONObject.parseObject(jsonObject2.toJSONString(), new TypeReference<Complex>() {});
System.out.println(complex1);//Complex{index=5, simples=[Simple{name='ttt', sex='male', age=12}, Simple{name='fff', sex='female', age=13}], grades=[12, 32, 43, 51]}
//JSON<=javabean
JSONObject jsonObject = JSONObject.parseObject(JSONObject.toJSONString(complexBean));
System.out.println(jsonObject.get("grades"));//[1,2,4,5,6]
System.out.println(jsonObject.get("simples"));//[{"sex":"male","name":"ggg","age":17},{"sex":"male","name":"ttt","age":18},{"sex":"male","name":"yyy","age":19}]
Json串 <==> javabean
//json串=>javabean，有两种方式
Complex complex = JSONObject.parseObject(complexJson, Complex.class);
System.out.println(complex);//Complex{index=5, simples=[Simple{name='ttt', sex='male', age=12}, Simple{name='fff', sex='female', age=13}], grades=[12, 32, 43, 51]}
Complex complex1 = JSONObject.parseObject(complexJson, new TypeReference<Complex>() {
});
System.out.println(complex1);
//json串<=javabean
String jsonString1 = JSONObject.toJSONString(complexBean);
System.out.println(jsonString1);//{"grades":[1,2,4,5,6],"index":1,"simples":[{"age":17,"name":"ggg","sex":"male"},{"age":18,"name":"ttt","sex":"male"},{"age":19,"name":"yyy","sex":"male"}]}
json数组
测试数据:
//javabean
static {
Simple simple0 = new Simple();
simple0.setAge(15);
simple0.setName("fff");
simple0.setSex("male");
Simple simple1 = new Simple();
simple1.setSex("female");
simple1.setAge(123);
simple1.setName("asdas");
arrayBean.add(simple0);
arrayBean.add(simple1);
}
//json串
public static String arrayJson = "[{\"name\": \"ttt\",\"age\": 12,\"sex\": \"male\"},{\"name\": \"fff\",\"age\": 13,\"sex\": \"female\"}]";
JSON <==> json串
//json==>JSON
JSONArray array = JSONArray.parseArray(arrayJson);
JSONObject object = array.getJSONObject(1);
System.out.println(object.get("sex"));//female
//json<==JSON
String json = JSONArray.toJSONString(array);
System.out.println(json);//[{"sex":"male","name":"ttt","age":12},{"sex":"female","name":"fff","age":13}]
JSON <==> javabean
//JSON==>javabean
JSONArray array = JSONArray.parseArray(arrayJson);
List<Simple> simples = JSONArray.parseArray(array.toJSONString(), Simple.class);
System.out.println(simples);//[Simple{name='ttt', sex='male', age=12}, Simple{name='fff', sex='female', age=13}]
//JSON<==javabean
JSONArray array1 = JSONArray.parseArray(JSONArray.toJSONString(arrayBean));
JSONObject object = array.getJSONObject(1);
System.out.println(object.get("sex"));//female
Json串 <==> javabean
//json=>javabean
//第一种方式
List<Simple> simples = JSONArray.parseArray(arrayJson, Simple.class);
System.out.println(simples);//[Simple{name='ttt', sex='male', age=12}, Simple{name='fff', sex='female', age=13}]
//第二种方式
JSONArray array = JSONArray.parseArray(arrayJson);
Type[] types = new Type[array.size()];
Arrays.fill(types, Map.class);
List<Object> simples1 = JSONArray.parseArray(arrayJson, types);
simples1.forEach(simples2 -> {
Map<String, Object> asd = (Map<String, Object>) simples2;
System.out.println(asd.get("name"));
});//ttt fff
//json<=javabean
String str = JSON.toJSONString(arrayBean);
System.out.println(str);//[{"age":15,"name":"fff","sex":"male"},{"age":123,"name":"asdas","sex":"female"}]
总结
整体测试下来，对于简单json和复杂json来说，其实两者没什么差别，其中转化过程中主要就是涉及到了JSONObject类，涉及到的方法就是JSONObject.parseObject()方法，它可以将string格式转为JSONObject或着bean对象。而对于JSONArray来说，也是大同小异，只不过是用JSONArray.parseArray()。另外还有一个方法，就是将bean转为String的函数：JSONObject.toJSONString(),JSONArray.toJSONString,JSON.toJSONString。看源码可以发现，前两者实际上都是在调用JSON.toJSONString()。总的来说，主要是这些东西，还是要在实际工作中不断应用总结。
