Recently took over a business installment payment is required by payment type , staging periods to find the corresponding rates . It involves the use of JSONObject and JSONArray.
Introduce fastjson dependency, The following code of copy and paste pom.xml <dependencies>... </dependencies>in
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.46</version>
</dependency>
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1. Business scenario application
The json string passed in by the installment payment service is as follows:
{
"花呗": [{
//分期支付产品类型
"instalmentNum": "6期", //分期的期数
"repaymentRate": "20.50%" //费率
}, {
"instalmentNum": "12期",
"repaymentRate": "25.00%"
}, {
"instalmentNum": "24期",
"repaymentRate": "13.00%"
}, {
"instalmentNum": "36期",
"repaymentRate": "18.00%"
}]
}
(The above values are made randomly, the key point is how to use JSONObject and JSONArray below)
Now I have to pay by installments type (a chant), staging periods (6) to find the corresponding rate of 20.50%
Remove Rate 20.50% steps:
- First get the value corresponding to Huabei: {"Huabei": value} The whole is a JSONObject, in the form of a key-value pair
- "Flower chant" corresponding to the value is a JSONArray,
形式如： [ {key:value}, {}, {} ], wherein the square brackets is the representative of a JSONArray, array inside each key-value pair is a form of {key: value}, is a type java.lang.Object
The project uses fastjson, so the following method is also based on this jar package
//入参repaymentRate是上面的那个json串
private static matchRepaymentRate(String repaymentRate){
//先拿到repaymentRate对应的json键值对形式{ "花呗": value }
JSONObject jsonObject=JSONObject.parseObject(repaymentRate);
//再拿到key(花呗)对应的value,是一个JSONArray，形如[{key:value},{..},{..}]
JSONArray jsonArray=jsonObject.getJSONArray("花呗");
for(int i=0;i<jsonArray.size();i++){
//得到数组的第i个元素,即{"instalmentNum": "6期","repaymentRate": "20.50%"}
JSONObject jsonObj= jsonArray.getJSONObject(i);
String instalmentNum=jsonObj.getString("instalmentNum");
if(instalmentNum.equals("6期")){
System.out.println("分期支付的类型是花呗 、分期6期得到的费率为："+jsonObj.getString("repaymentRate"));
}
}
}
Payment type (some chant) + 6 installments => the rate is 20.50%, the result is as follows
Second, JSONObject
JSONObject is a key-value pair, which is shaped like {key: value }. Later, when you see {} braces, it can be regarded as a JSONObject.
itThe inside is actually a Map<String, Object> map, Can be HashMap, or LinkedHashMap
Construction method
- Default construction: What you get is a HashMap with an initial capacity of 16,
public JSONObject() { this(16, false); }where false is to construct a HashMap, and true is to construct a LinkedHashMap - The artificial designation is to construct a HashMap or a LinkedHashMap (but the initial capacity cannot be specified):
public JSONObject(boolean ordered) { this(16, ordered); } - Manually specify the capacity of HashMap (not LinkedHashMap):
public JSONObject(int initialCapacity) - At the same time, the initial capacity and container type can be specified:
public JSONObject(int initialCapacity, boolean ordered) {
if (ordered) {
this.map = new LinkedHashMap(initialCapacity);
} else {
this.map = new HashMap(initialCapacity);
}
}
JSONObject commonly used API
public Object get(Object key): Called the Map.get(key) methodpublic JSONObject getJSONObject(String key): Obtaining a JSONObject object because Map <Stirng, Object> value is the Object, so return to cast JSONObject , i.e. (JSONObject) valuepublic JSONArray getJSONArray(String key): Get a JSONArray array, the method will return a (JSONArray) map.get(key)
There are other getString(String key) and getDouble(String key) that convert the Object value to the corresponding type and return
Three, JSONArray
JSONArray is essentially one List<Object>, and the following API is also based on List operations
Construction method
There are three construction methods:
- Default structure:
public JSONArray() { this.list = new ArrayList(); } - The structure of a List collection can be passed in:
public JSONArray(List<Object> list) { this.list = list; } - JSONArray(int initialCapacity) Set the initial capacity of the List
JSONArray commonly used API
JSONObject getJSONObject(int index)Obtain the element at the specified position, using forced type conversion: (JSONObject) list.get(index)JSONArray getJSONArray(int index): The element at the specified position obtained is (JSONArray) list.get(index), a JSONArray arrayString getString(int index): Return the element at the specified position, and turn the original Object element into a String elementJSONArray getJSONArray(int index): Obtaining inner nested in JSON array, such that:
{
"成绩排名":[ //外层json数组
{
"第一名":[{
"姓名":"小明"},{
"学号":"1"}] //内层json数组
},{
"第二名":[{
"姓名":"二狗子"},{
"学号":"2"}]
}
]
}
There are 2 levels of JSONArray nested in the json string, with 2 levels of square brackets []. If
I want to know who is the first, the operation is as follows:
String str ="{\"成绩排名\": ... }"
JSONObject jsonObject=JSON.parseObject(str);
//拿到了外层json数组：[{"第一名":[{"姓名":"小明"},{"学号":"1"}]}, {..}]
JSONArray jsonArray=jsonObject.getJSONArray("成绩排名");
for(int i=0;i<jsonArray.size();i++){
JSONObject jsonObj=jsonArray.getJSONObject(i);
//拿到了内层的json数组：[{"姓名":"小明"},{"学号":"1"}]
JSONArray jsonArr =jsonObj.getJSONArray("第一名");
for(int j=0;jsonArr!=null&&j<jsonArr.size();j++){
//拿到了JSONObject {"姓名":"小明"}
JSONObject json =jsonArr.getJSONObject(j);
System.out.println(json.getString("姓名"));
}
}
Use of JSONObject and JSONArray
(1) Add key-value pairs to a json object, and add json objects to the JSONArray array
//json添加键值对
JSONObject jsonObject=new JSONObject();
jsonObject.put("key","value");
//在JSONArray添加json对象
JSONArray jsonArray=new JSONArray();
jsonArray.add(jsonObject);
(2) Convert String type json string to JSONObject and JSONArray
① Convert String to JSONObject
String str = "{ \"name\":\"小明\" }";
JSONObject jsonObject=JSON.parseObject(str);
② Convert String to JSONArray
String str = "[{ \"name\":\"小明\" }]";
JSONArray jsonArray=JSON.parseArray(str);
System.out.println( jsonArray.getJSONObject(0));
Output: { "name": "Bob"}, if not json string "[]" brackets, it is unable to obtain the element from the specified location , either jsonArray.get (0) or jsonArray.getJSONObject (0 ) Will throw an exception, without square brackets [], the format is incorrect.