将JSON数据转换成JAVA的实体类

思路：首先将JSON格式的数据转换成JSONObject，然后将JSONObject转换成Java的实体类（其中类属性包括List等类型）

Java实体类：

SearchFilter 类

 1 public class SearchFilter {
 2     private String groupOp;
 3     
 4     private List<SearchRule> rules;
 5 
 6     public String getGroupOp() {
 7         return groupOp;
 8     }
 9 
10     public void setGroupOp(String groupOp) {
11         this.groupOp = groupOp;
12     }
13 
14     public List<SearchRule> getRules() {
15         return rules;
16     }
17 
18     public void setRules(List<SearchRule> rules) {
19         this.rules = rules;
20     }

SearchRule 类：

 1 public class SearchRule {
 2     private String field;
 3     private String op;
 4     private String data;
 5     public String getField() {
 6         return field;
 7     }
 8     public void setField(String field) {
 9         this.field = field;
10     }
11     public String getOp() {
12         return op;
13     }
14     public void setOp(String op) {
15         this.op = op;
16     }
17     public String getData() {
18         return data;
19     }
20     public void setData(String data) {
21         this.data = data;
22     }
23 
24 
25 }

1 //导入的package
2 import com.fasterxml.jackson.databind.ObjectMapper;
3 import net.sf.json.JSONArray;
4 import net.sf.json.JSONObject;

解析JSon格式字符串的方法

 1 public SearchFilter jsonToSearchFilter(String filters) {
 2         SearchFilter searchFilter = null;
 3         try {
 4             JSONObject jsonobject = JSONObject.fromObject(filters);//将json格式的字符串转换成JSONObject 对象
 5             JSONArray array = jsonobject.getJSONArray("rules");    //如果json格式的字符串里含有数组格式的属性，将其转换成JSONArray，以方便后面转换成对应的实体
 6             List<SearchRule> rules = new ArrayList<SearchRule>();
 7             for (int i = 0; i < array.size(); i++) {
 8                 JSONObject object = (JSONObject) array.get(i);     //将array中的数据进行逐条转换
 9                 SearchRule rule = (SearchRule) JSONObject.toBean(object, SearchRule.class);  //通过JSONObject.toBean()方法进行对象间的转换
10                 rules.add(rule);
11             }
12             String groupOp = jsonobject.getString("groupOp");  //简单的直接获取值
13             searchFilter = new SearchFilter();                 //对SearchFilter对象进行组装
14             searchFilter.setGroupOp(groupOp);
15             searchFilter.setRules(rules);
16         } catch (Exception e) {
17             System.out.println("filters=" + filters.toString() + ".json转换成实体类出错");
18             e.printStackTrace();
19         }
20         return searchFilter;
21     }

这里只进行了SearchFilter类中list<SearchRule>rule属性的对象转换，因为它是一个SearchRule对象数组，需要单独拿出来进行json转换成对象，如果直接对filter进行 SearchFilter进行实体转换会报错。如果对象中不含有list,array，map等集合，可以像8-9行一样进行对象转换。

测试：

1 public static void main(String[] args) {
2         UserMgmtController con = new UserMgmtController();
3         String filters="{"groupOp": "OR","rules": [{"field": "realname","op": "eq","+
4                        ""data": "1234"},{"field": "cityCode","op": "ne","data": "5678"}]}";
5         SearchFilter searchFilter =con.jsonToSearchFilter(filters);
6         System.out.println("gop="+searchFilter.getGroupOp()+" rules.size="+searchFilter.getRules().size());
7     }
结果：gop=OR rules.size=2

将java对象转换成json格式：

 1 //将Object 对象转换成 json
 2     public String objectToJson(Object obj) {
 3         ObjectMapper mapper = new ObjectMapper();
 4         // Convert object to JSON string
 5         String jsonStr = null;
 6         try {
 7             jsonStr = mapper.writeValueAsString(obj);
 8         } catch (IOException e) {
 9             log.error(obj + "entity 轉換成 json出錯", e);
10             e.printStackTrace();
11             System.out.println("entity 轉換成 json出錯");
12         }
13         return jsonStr;
14     }

将Object 转换成json字符串时，默认使用用是的驼峰方式，如果不想使用驼峰则可以增加红色部分设置，带下划线的也可以原样输出：

 1 public String objectToJson(Object obj){
 2         ObjectMapper mapper = new ObjectMapper();
 3         String json =null;
 4         try {
 5             PropertyNamingStrategy.PascalCaseStrategy pp = new PropertyNamingStrategy.PascalCaseStrategy();            
 6             mapper.setPropertyNamingStrategy(pp);
 7             json = mapper.writeValueAsString(obj);
 8         } catch (JsonProcessingException e) {
 9             log.error("json对象转换失败",e);
10             e.printStackTrace();
11         }
12         return json;
13     }

结果：

"UpLoadDateTime":"2017-09-25 10:51:41","OrganizationId":"B3EA5A4D-7C60-4C21-AF09-494890467C34" ，"Test_Code":""