java下划线与驼峰命名互转

Posted 2021-01-25 学不死的程序员

方式一：

下划线与驼峰命名转换：

public class Tool {
  private static Pattern linePattern = Pattern.compile("_(\w)");
 
 /** 下划线转驼峰 */
  public static String lineToHump(String str) {
        str = str.toLowerCase();
     Matcher matcher = linePattern.matcher(str);
      StringBuffer sb = new StringBuffer();
      while (matcher.find()) {
          matcher.appendReplacement(sb, matcher.group(1).toUpperCase());
     }
       matcher.appendTail(sb);
     return sb.toString();
 }
 
  /** 驼峰转下划线(简单写法，效率低于{@link #humpToLine2(String)}) */
 public static String humpToLine(String str) {
       return str.replaceAll("[A-Z]", "_$0").toLowerCase();
    }
 
  private static Pattern humpPattern = Pattern.compile("[A-Z]");
 
    /** 驼峰转下划线,效率比上面高 */
  public static String humpToLine2(String str) {
      Matcher matcher = humpPattern.matcher(str);
     StringBuffer sb = new StringBuffer();
     while (matcher.find()) {
          matcher.appendReplacement(sb, "_" + matcher.group(0).toLowerCase());
      }
       matcher.appendTail(sb);
     return sb.toString();
 }
 
  public static void main(String[] args) {
      String lineToHump = lineToHump("f_parent_no_leader");
      System.out.println(lineToHump);// fParentNoLeader
     System.out.println(humpToLine(lineToHump));// f_parent_no_leader
      System.out.println(humpToLine2(lineToHump));// f_parent_no_leader
 }
}

不纠结""_"+matcher.group(0).toLowerCase()"的话，humpToLine2效率会比humpToLine高一些，看String#replaceAll方法源码即可。

方式二：

实体类：

 1 import java.io.Serializable;
 2 import lombok.AllArgsConstructor;
 3 import lombok.Data;
 4 import lombok.NoArgsConstructor;
 5 
 6 @Data
 7 @AllArgsConstructor
 8 @NoArgsConstructor
 9 public class User implements Serializable {
10     /**
11      * 
12      */
13     private static final long serialVersionUID = -329066647199569031L;
14     
15     private String userName;
16     
17     private String orderNo;
18 }

帮助类：

 1 import java.io.IOException;
 2 
 3 import com.fasterxml.jackson.annotation.JsonInclude.Include;
 4 import com.fasterxml.jackson.core.JsonProcessingException;
 5 import com.fasterxml.jackson.databind.ObjectMapper;
 6 import com.fasterxml.jackson.databind.PropertyNamingStrategy;
 7 
 8 /**
 9  * JSON的驼峰和下划线互转帮助类
10  * 
11  * @author yangzhilong
12  *
13  */
14 public class JsonUtils {
15 
16     /**
17      * 将对象的大写转换为下划线加小写，例如：userName-->user_name
18      * 
19      * @param object
20      * @return
21      * @throws JsonProcessingException
22      */
23     public static String toUnderlineJSONString(Object object) throws JsonProcessingException{
24         ObjectMapper mapper = new ObjectMapper();
25         mapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
26         mapper.setSerializationInclusion(Include.NON_NULL);      
27         String reqJson = mapper.writeValueAsString(object);
28         return reqJson;
29     }
30 
31     /**
32      * 将下划线转换为驼峰的形式，例如：user_name-->userName
33      * 
34      * @param json
35      * @param clazz
36      * @return
37      * @throws IOException
38      */
39     public static <T> T toSnakeObject(String json, Class<T> clazz) throws IOException{
40         ObjectMapper mapper = new ObjectMapper();
　　        // mapper的configure方法可以设置多种配置（例如：多字段 少字段的处理）
　　　　　　 //mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

41         mapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
42         T reqJson =  mapper.readValue(json, clazz);
43         return reqJson;
44     }
45 }

单元测试类：

 1 import java.io.IOException;
 2 
 3 import org.junit.Test;
 4 
 5 import com.alibaba.fastjson.JSONObject;
 6 import com.fasterxml.jackson.core.JsonProcessingException;
 7 
 8 public class JsonTest {
 9     
10     @Test
11     public void testToUnderlineJSONString(){
12         User user = new User("张三", "1111111");
13         try {
14             String json = JsonUtils.toUnderlineJSONString(user);
15             System.out.println(json);
16         } catch (JsonProcessingException e) {
17             e.printStackTrace();
18         }
19     }
20     
21     @Test
22     public void testToSnakeObject(){
23         String json = "{"user_name":"张三","order_no":"1111111"}";
24         try {
25             User user = JsonUtils.toSnakeObject(json, User.class);
26             System.out.println(JSONObject.toJSONString(user));
27         } catch (IOException e) {
28             e.printStackTrace();
29         }
30     }
31 }

测试结果：

1 {"user_name":"张三","order_no":"1111111"}
2 
3 {"orderNo":"1111111","userName":"张三"}