java下划线与驼峰命名互转

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：

import java.io.Serializable;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = -329066647199569031L;
    
    private String userName;
    
    private String orderNo;
}

帮助类：

import java.io.IOException;

import com.fasterxml.jackson.annotation.JsonInclude.Include;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategy;

/**
 * JSON的驼峰和下划线互转帮助类
 * 
 * @author yangzhilong
 *
 */
public class JsonUtils {

    /**
     * 将对象的大写转换为下划线加小写，例如：userName-->user_name
     * 
     * @param object
     * @return
     * @throws JsonProcessingException
     */
    public static String toUnderlineJSONString(Object object) throws JsonProcessingException{
        ObjectMapper mapper = new ObjectMapper();
        mapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
        mapper.setSerializationInclusion(Include.NON_NULL);      
        String reqJson = mapper.writeValueAsString(object);
        return reqJson;
    }

    /**
     * 将下划线转换为驼峰的形式，例如：user_name-->userName
     * 
     * @param json
     * @param clazz
     * @return
     * @throws IOException
     */
    public static <T> T toSnakeObject(String json, Class<T> clazz) throws IOException{
        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);

        mapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
        T reqJson =  mapper.readValue(json, clazz);
        return reqJson;
    }
}

单元测试类：

import java.io.IOException;

import org.junit.Test;

import com.alibaba.fastjson.JSONObject;
import com.fasterxml.jackson.core.JsonProcessingException;

public class JsonTest {
    
    @Test
    public void testToUnderlineJSONString(){
        User user = new User("张三", "1111111");
        try {
            String json = JsonUtils.toUnderlineJSONString(user);
            System.out.println(json);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
    }
    
    @Test
    public void testToSnakeObject(){
        String json = "{"user_name":"张三","order_no":"1111111"}";
        try {
            User user = JsonUtils.toSnakeObject(json, User.class);
            System.out.println(JSONObject.toJSONString(user));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

测试结果：

{"user_name":"张三","order_no":"1111111"}

{"orderNo":"1111111","userName":"张三"}