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java巧用@Convert實(shí)現(xiàn)表字段自動(dòng)轉(zhuǎn)entity

更新時(shí)間：2024年07月26日 09:27:45 作者：螺螄小公雞

本文主要介紹了java巧用@Convert實(shí)現(xiàn)表字段自動(dòng)轉(zhuǎn)entity,文中通過(guò)示例代碼介紹的非常詳細(xì),對(duì)大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值,需要的朋友們下面隨著小編來(lái)一起學(xué)習(xí)學(xué)習(xí)吧

1.背景

本人自入職以來(lái)，接了一堆歷史包(shi)袱(shan)，其中有個(gè)服務(wù)是基于MongoDB實(shí)現(xiàn)的，而公司要搞信創(chuàng)化，去掉MongoDB是遲早的事，于是便開(kāi)始分析底層數(shù)據(jù)結(jié)構(gòu)，計(jì)劃用pg替換MongoDB。

2.難點(diǎn)

2.1 數(shù)據(jù)結(jié)構(gòu)不同

MongoDB是文檔型數(shù)據(jù)庫(kù)，而pg是關(guān)系型數(shù)據(jù)庫(kù)，原項(xiàng)目MongoDB的collection中某些字段類型為L(zhǎng)ist或者entity，存在一對(duì)多的情況，如果采用新建關(guān)聯(lián)表的方式，會(huì)增加數(shù)據(jù)結(jié)構(gòu)復(fù)雜性，且底層數(shù)據(jù)幾乎不會(huì)變，因此，覺(jué)得直接用VARCHAR類型存儲(chǔ)List類型的json串。

2.2 數(shù)據(jù)類型轉(zhuǎn)換

服務(wù)的數(shù)據(jù)庫(kù)持久化使用的是jpa，原來(lái)MongoDB類型會(huì)自動(dòng)轉(zhuǎn)成List，如下列的options屬性

@Data
@Document(collection = "input_item")
public class InputItem implements Comparable<InputItem> {

   @Id
   private String itemCode;
   
   private String title;
   private String description;
   private int itemType;
   private List<InputItemOption> options;
   private String defaultOptionNum;
   private String unit;
   private boolean whetherActive;
}

轉(zhuǎn)成pg后，options字段在數(shù)據(jù)庫(kù)中是String類型，需要轉(zhuǎn)成List。經(jīng)過(guò)調(diào)研，可以采用自定義Converter+注解@Convert來(lái)實(shí)現(xiàn)。

2.2.1 List類型

1）自定義Converter

import com.alibaba.fastjson.JSON;
import javax.persistence.AttributeConverter;
/**
 * @ClassName JpaConverterListJson
 * @Description jpa list轉(zhuǎn)換為String 相互轉(zhuǎn)換工具類
 * @Author ygt
 * @Date 2021/3/3 14:49
 * @Version V1.0
 */
public class JpaConverterListJson  implements AttributeConverter<Object, String> {
    @Override
    public String convertToDatabaseColumn(Object o) {
        return JSON.toJSONString(o);
    }

    @Override
    public Object convertToEntityAttribute(String s) {
        return JSON.parseArray(s);
    }
}

2）@Convert注解

import java.util.List;
import com.fasterxml.jackson.annotation.JsonInclude;
import io.swagger.annotations.ApiModel;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.NoArgsConstructor;

import lombok.Data;

import javax.persistence.*;

/**
 * 
 * @Description 輸入項(xiàng)實(shí)體類
 *
 */
@ApiModel("")
@JsonInclude(value = JsonInclude.Include.NON_NULL)
@Table(name = "input_item")
@Builder
@AllArgsConstructor
@NoArgsConstructor
@Data
@Entity
public class InputItem implements Comparable<InputItem> {

   @GeneratedValue
   @Column(name = "id")
   @Id
   private String itemCode;

   @Column(name = "title")
   private String title;
   @Column(name = "description")
   private String description;
   @Column(name = "itemtype")
   private int itemType;

   @Convert(converter = JpaConverterListJson.class)
   private List<InputItemOption> options;
   @Column(name = "defaultoptionnum")
   private String defaultOptionNum;
   @Column(name = "unit")
   private String unit;
   @Column(name = "whetheractive")
   private Boolean whetherActive;

   @Override
   public int compareTo(InputItem o) {
      int index1 = Integer.parseInt(this.itemCode.substring(this.itemCode.lastIndexOf('_') + 1));
      int index2 = Integer.parseInt(o.itemCode.substring(o.itemCode.lastIndexOf('_') + 1));
      if (index1 < index2) {
         return -1;
      }
      else {
         return 1;
      }
   }
}

2.2.2 entity類型

1）自定義Converter

import com.alibaba.fastjson.JSON;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.test.src.domain.index.interest.InterestCreditScoreSection;

import javax.persistence.AttributeConverter;
import java.lang.reflect.ParameterizedType;

/**
 * @ClassName JpaConverterListJson
 * @Description jpa 泛型T轉(zhuǎn)換為String 相互轉(zhuǎn)換工具類
 * @Author ygt
 * @Date 2021/3/3 14:49
 * @Version V1.0
 */
public class JpaConverterObjectJson<T> implements AttributeConverter<T, String> {

    private static final ObjectMapper objectMapper = new ObjectMapper();

    @Override
    public String convertToDatabaseColumn(T o) {
        try {
            return objectMapper.writeValueAsString(o);
        } catch (Exception e) {
            throw new RuntimeException("Failed to convert object to string", e);
        }
    }

    @Override
    public T convertToEntityAttribute(String s) {
        try {
            return objectMapper.readValue(s, (Class<T>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0]);
        } catch (Exception e) {
            throw new RuntimeException("Failed to convert string to object", e);
        }
    }
}

import com.test.src.domain.index.interest.InterestCreditScoreSection;

public class InterestCreditScoreSectionConverter extends JpaConverterObjectJson<InterestCreditScoreSection>{
}

2）@Convert注解

import com.fasterxml.jackson.annotation.JsonInclude;
import com.test.src.utils.InterestCreditScoreSectionConverter;
import io.swagger.annotations.ApiModel;
import lombok.NoArgsConstructor;

import lombok.*;

import javax.persistence.*;

/**
 * 
 * @Description 利率授信實(shí)體類
 */
@ApiModel("")
@JsonInclude(value = JsonInclude.Include.NON_NULL)
@Table(name = "interest_credit")
@Builder
@AllArgsConstructor
@NoArgsConstructor
@Data
@Entity
public class InterestCredit {

   @Id
   @GeneratedValue
   @Column(name = "id")
   private String itemNo;

   @Column(name = "recommendinterestformula")
   private String recommendInterestFormula; //推薦執(zhí)行利率計(jì)算公式;

   @Convert(converter = InterestCreditScoreSectionConverter.class)
   @Column(name = "interestcreditscoresection")
   private InterestCreditScoreSection interestCreditScoreSection;
}

3.總結(jié)

針對(duì)不好處理的json string類型，可通過(guò)自定義converter+@Convert的方式實(shí)現(xiàn)自動(dòng)轉(zhuǎn)換，另外，可在自定義converter類上加@Convert(autoApply = true)實(shí)現(xiàn)全局自動(dòng)轉(zhuǎn)換。

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