MapStruct 使用 defaultExpression

使用 Mapstruct 我们可以使用 defaultExpression 传递一个计算值，以防源属性为空，使用 @Mapping 注解的 defaultExpression 属性。

语法

@Mapping(target = "target-property", source="source-property" defaultExpression = "default-value-method")

• default-value-method 如果 source-property 为 null，则 target-property 将设置为 default-value-method 的结果。

示例

打开 使用 defaultValue 进行映射 一章中更新的项目映射。

使用以下代码更新 CarEntity.java

CarEntity.java

package com.jiyik.entity;

import java.util.GregorianCalendar;

public class CarEntity {
    private int id;
    private double price;
    private GregorianCalendar manufacturingDate;
    private String name;
    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;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

使用以下代码更新 Car.java

Car.java

package com.jiyik.model;

public class Car {
    private int id;
    private String price;
    private String manufacturingDate;
    private String brand;
    private String name;
    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;
    }
    public String getBrand() {
        return brand;
    }
    public void setBrand(String brand) {
        this.brand = brand;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

使用以下代码更新 CarMapper.java

CarMapper.java

package com.jiyik.mapper;

import com.jiyik.entity.CarEntity;
import com.jiyik.model.Car;
import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

@Mapper
public interface CarMapper {
    @Mapping(source = "name", target = "name", defaultExpression = "java(UUID.randomUUID().toString())")
    @Mapping(target = "brand", constant = "BMW")
    @Mapping(source = "price", target = "price", numberFormat = "$#.00")
    @Mapping(source = "manufacturingDate", target = "manufacturingDate", dateFormat = "dd.MM.yyyy")
    Car getModelFromEntity(CarEntity carEntity);
}

使用以下代码更新 CarMapperTest.java

CarMapperTest.java

import com.jiyik.entity.CarEntity;
import com.jiyik.mapper.CarMapper;
import com.jiyik.model.Car;
import org.junit.Test;
import org.mapstruct.factory.Mappers;

import java.util.GregorianCalendar;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

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());
        assertNotNull(model.getName());
        assertEquals("BMW", model.getBrand());
    }
}

运行以下命令来测试映射。

$ mvn clean test

执行结果如下