MapStruct - 使用表达式

MapStruct 允许为自定义逻辑调用转换方法。我们可以使用表达式来实现相同的功能，其中我们可以传递任何 Java 对象并调用其方法来进行转换。

语法

@Mapping(target = "target-property", 
   expression = "java(target-method())")

这里

• 目标属性 - 我们正在进行映射的属性。

• 表达式 - 映射器将调用表达式中编写的 Java 方法。

• 目标方法 - 目标方法是要调用的方法。如果方法存在于不同的类中，则使用 new 类名.目标方法()

示例

在 Eclipse 中打开在 使用 dateFormat 映射 章节中更新的项目映射。

使用以下代码更新 CarEntity.java -

CarEntity.java

package com.tutorialspoint.entity;
import java.util.GregorianCalendar;

public class CarEntity {
   private int id;
   private double price;
   private GregorianCalendar manufacturingDate;
   public int getId() {
      return id;
   }
   public void setId(int id) {
      this.id = id;
   }
   public double getPrice() {
      return price;
   }
   public void setPrice(double price) {
      this.price = price;
   }
   public GregorianCalendar getManufacturingDate() {
      return manufacturingDate;
   }
   public void setManufacturingDate(GregorianCalendar manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
}

使用以下代码更新 Car.java -

Car.java

package com.tutorialspoint.model;

public class Car {
   private int id;
   private String price;
   private String manufacturingDate;
   public int getId() {
      return id;
   }
   public void setId(int id) {
      this.id = id;
   }
   public String getPrice() {
      return price;
   }
   public void setPrice(String price) {
      this.price = price;
   }
   public String getManufacturingDate() {
      return manufacturingDate;
   }
   public void setManufacturingDate(String manufacturingDate) {
      this.manufacturingDate = manufacturingDate;
   }
}

使用以下代码更新 CarMapper.java -

CarMapper.java

package com.tutorialspoint.mapper;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.GregorianCalendar;
import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.model.Car;

@Mapper
public interface CarMapper {
   @Mapping(source = "price", target = "price", numberFormat = "$#.00")
   @Mapping(target = "manufacturingDate", 
      expression = "java(getManufacturingDate(carEntity.getManufacturingDate()))")
   Car getModelFromEntity(CarEntity carEntity);

   default String getManufacturingDate(GregorianCalendar manufacturingDate) {
      Date d = manufacturingDate.getTime();
      SimpleDateFormat sdf = new SimpleDateFormat( "dd.MM.yyyy" );
      return sdf.format( d );
   }
}

使用以下代码更新 CarMapperTest.java -

CarMapperTest.java

package com.tutorialspoint.mapping;

import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.GregorianCalendar;
import org.junit.jupiter.api.Test;
import org.mapstruct.factory.Mappers;
import com.tutorialspoint.entity.CarEntity;
import com.tutorialspoint.mapper.CarMapper;
import com.tutorialspoint.model.Car;

public class CarMapperTest {
   private CarMapper carMapper = Mappers.getMapper(CarMapper.class);

   @Test
   public void testEntityToModel() {
      CarEntity entity = new CarEntity();
      entity.setPrice(345000);
      entity.setId(1);
      entity.setManufacturingDate(new GregorianCalendar(2015, 3, 5));
      Car model = carMapper.getModelFromEntity(entity);
      assertEquals(model.getPrice(), "$345000.00");
      assertEquals(entity.getId(), model.getId());
      assertEquals("05.04.2015", model.getManufacturingDate());
   }
}

运行以下命令来测试映射。

mvn clean test

输出

命令成功后。验证输出。

mvn clean test
[INFO] Scanning for projects...
...
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ mapping ---
[INFO] Surefire report directory: \mvn\mapping\target\surefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.tutorialspoint.mapping.CarMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.035 sec
Running com.tutorialspoint.mapping.DeliveryAddressMapperTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 sec
Running com.tutorialspoint.mapping.StudentMapperTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

Results :

Tests run: 4, Failures: 0, Errors: 0, Skipped: 0
...