Gson系列4 --- 政策篇 -- FieldNamingStrategy

1、簡述

[FieldNamingStrategy]  
屬性命名政策 --
   用于自定義 json  key 的形式 
   new GsonBuilder()
     // 采用自定義的政策
    .setFieldNamingStrategy(new FieldStrategy.AllUpperCaseStrategy())
    // 采用 預設類的政策
    .setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_DOTS)
    .create();
   -- 注意： 隻能有一個政策起作用。
         

2、實體類

實作以下功能 ① 讓屬性的名稱 全部改為大寫，

如 username ---->  USERNAME

  userId ---->  USERID

或者 實作 在屬性名的前後面 加上字首 或字尾

注解類如下

package sun.rain.amazing.gson.strategy.field;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * 采用注解的用于改變 對應的key值
 * @author Reese
 */
@Target( ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface GsonKeyValue {
    String value() default "";
    String prefix() default "";
    String suffix() default "";

}
      

給屬性添加字首 或字尾

@GsonKeyValue(prefix = "CN_", suffix = "_AN")
      

private String mobile;

變成  mobile  --->   CN_mobile_AN:  "xxx"

package sun.rain.amazing.gson.strategy.field;

import com.google.gson.FieldNamingStrategy;

import java.lang.reflect.Field;

/**
 * 命名政策
 * @author sunRainAmazing
 */
public class FieldStrategy {

    /**
     * 采用全部大寫的形式
  */
    public static class AllUpperCaseStrategy implements FieldNamingStrategy{
        @Override
        public String translateName(Field f) {
            return f.getName().toUpperCase();
        }
    }

    /**
     * 添加前置 和 後置 注解
  */
    public static class GsonKeyValueCaseStrategy implements FieldNamingStrategy{
        @Override
        public String translateName(Field f) {
            GsonKeyValue gkv = f.getAnnotation(GsonKeyValue.class);
            if(gkv != null){
                if(gkv.value().length()>0){
                    return gkv.prefix() + gkv.value() + gkv.suffix();
                }else{
                    return gkv.prefix() + f.getName() + gkv.suffix();
                }
            }else{
                return f.getName();
            }

        }
    }
}
      

實體類

@Data
@AllArgsConstructor
@NoArgsConstructor
public class GsonField {
    private Integer id;
    @SerializedName("user_name")
    private String name;
    private String email;
}      

package sun.rain.amazing.gson.strategy.field;

import com.google.gson.annotations.SerializedName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * @author sunRainAmazing
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
public class GsonFieldKey {
    private Integer id;
    @SerializedName("user_name")
    private String name;
    @GsonKeyValue(prefix = "QQ_")
    private String email;
    @GsonKeyValue(prefix = "CN_", suffix = "_AN")
    private String mobile;
    @GsonKeyValue(value="desc_info", prefix = "CN_", suffix = "_AN")
    private String extra;
}
      

3、測試類

package sun.rain.amazing.gson.strategy;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import org.junit.Test;
import sun.rain.amazing.gson.strategy.field.FieldStrategy;
import sun.rain.amazing.gson.strategy.field.GsonField;
import sun.rain.amazing.gson.strategy.field.GsonFieldKey;

/**
 * @author sunRainAmazing
 */
public class GsonFieldTest {

    Gson gson = new Gson();


    /**
     * 預設注解 優先級 高于自定義的 屬性名政策
  *     {"ID":10,  "user_name":"tom",  "EMAIL":"[email protected]"}
     *   GsonField(id=10, name=tom, [email protected])
     */
    @Test
    public void test(){
        GsonField g = new GsonField(10,"tom","[email protected]");

        gson = new GsonBuilder()
                .setFieldNamingStrategy(new FieldStrategy.AllUpperCaseStrategy())
                .create();
        String json = gson.toJson(g);
        System.out.println(json);

        g = gson.fromJson(json,GsonField.class);
        System.out.println(g);
    }

    /**
     * 隻能有一個命名政策起作用
     * {"id":10,"user_name":"tom","QQ_email":"[email protected]",
     *              "CN_mobile_AN":"12025",
     *              "CN_desc_info_AN":"this is some message"}
     *
     * GsonFieldKey(id=10, name=tom, [email protected], mobile=12025,
     *              extra=this is some message)
     */
    @Test
    public void test1(){
        GsonFieldKey g = new GsonFieldKey(10,"tom","[email protected]"
        ,"12025","this is some message");

        gson = new GsonBuilder()
                .setFieldNamingStrategy(new FieldStrategy.AllUpperCaseStrategy())
                .setFieldNamingStrategy(new FieldStrategy.GsonKeyValueCaseStrategy())
                .create();
        String json = gson.toJson(g);
        System.out.println(json);

        g = gson.fromJson(json,GsonFieldKey.class);
        System.out.println(g);
    }




}