新建实体类User

package com.mmh.epeius.server.javabase.mapstruct;
import lombok.Data;
import lombok.experimental.Accessors;
import java.time.LocalDate;
import java.time.LocalDateTime;
 * @author : maominghai
 * @date : 2021/6/27 14:10
@Data
@Accessors(chain = true)
public class User {
    private Long id;
    private String username;
    private String password; // 密码
    private Integer sex;  // 性别
    private LocalDate birthday; // 生日
    private LocalDateTime createTime; // 创建时间
    private String config; // 其他扩展信息，以JSON格式存储
新建VO类 UserVo
package com.mmh.epeius.server.javabase.mapstruct;
import lombok.Data;
import lombok.experimental.Accessors;
import java.time.LocalDate;
import java.util.List;
 * @author : maominghai
 * @date : 2021/6/27 14:11
@Data
@Accessors(chain = true)
public class UserVo {
    private Long id;
    private String username;
    private String password;
    private Integer gender;
    private LocalDate birthday;
    private String createTime;
    private List<UserConfig> config;
    @Data
    public static class UserConfig {
        private String field1;
        private Integer field2;
新增映射接口，里面可以写很多的java bean 转化的映射方法，参数是source ，返回值是 target，@Mapping里面写映射关系，如下所示
package com.mmh.epeius.server.javabase.mapstruct;
import com.alibaba.fastjson.JSON;
import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.factory.Mappers;
import java.util.List;
 * @author : maominghai
 * @date : 2021/6/27 14:12
@Mapper
public interface UserConverter {
    UserConverter INSTANCE = Mappers.getMapper(UserConverter.class);
    @Mapping(target = "gender", source = "sex")
    @Mapping(target = "createTime", dateFormat = "yyyy-MM-dd HH:mm:ss")
    UserVo do2vo(User var1);
    @Mapping(target = "sex", source = "gender")
    @Mapping(target = "password", ignore = true)
    @Mapping(target = "createTime", dateFormat = "yyyy-MM-dd HH:mm:ss")
    User vo2Do(UserVo var1);
    List<UserVo> do2voList(List<User> userList);
    default List<UserVo.UserConfig> strConfigToListUserConfig(String config) {
        return JSON.parseArray(config, UserVo.UserConfig.class);
    default String listUserConfigToStrConfig(List<UserVo.UserConfig> list) {
        return JSON.toJSONString(list);
新增测试类，进行测试
package com.mmh.epeius.server.javabase;
import com.mmh.epeius.server.javabase.mapstruct.User;
import com.mmh.epeius.server.javabase.mapstruct.UserConverter;
import com.mmh.epeius.server.javabase.mapstruct.UserVo;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.util.Collections;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.testng.AssertJUnit.assertNotNull;
 * @author : maominghai
 * @date : 2021/6/27 14:16
@RunWith(SpringRunner.class)
@SpringBootTest
public class MapStructTest {
    @Test
    public void do2VoTest() {
        User user = new User()
                .setId(1L)
                .setUsername("zhangsan")
                .setSex(1)
                .setPassword("abc123")
                .setCreateTime(LocalDateTime.now())
                .setBirthday(LocalDate.of(1999, 9, 27))
                .setConfig("[{\"field1\":\"Test Field1\",\"field2\":500}]");
        UserVo userVo = UserConverter.INSTANCE.do2vo(user);
        // asset
        assertNotNull(userVo);
        assertEquals(userVo.getId(), user.getId());
        // print
        System.out.println(user);
        System.out.println(userVo);
//        User(id=1, username=zhangsan, password=abc123, sex=1, birthday=1999-09-27, createTime=2020-08-17T14:54:01.528, config=[{"field1":"Test Field1","field2":500}])
//        UserVo(id=1, username=zhangsan, password=abc123, gender=1, birthday=1999-09-27, createTime=2020-08-17 14:54:01, config=[UserVo.UserConfig(field1=Test Field1, field2=500)])
    @Test
    public void vo2DoTest() {
        UserVo.UserConfig userConfig = new UserVo.UserConfig();
        userConfig.setField1("Test Field1");
        userConfig.setField2(500);
        UserVo userVo = new UserVo()
                .setId(1L)
                .setUsername("zhangsan")
                .setGender(2)
                .setCreateTime("2020-01-18 15:32:54")
                .setBirthday(LocalDate.of(1999, 9, 27))
                .setConfig(Collections.singletonList(userConfig));
        User user = UserConverter.INSTANCE.vo2Do(userVo);
        // asset
        assertNotNull(userVo);
        assertEquals(userVo.getId(), user.getId());
        // print
        System.out.println(user);
        System.out.println(userVo);
不出意外，代码报错：
java.lang.ExceptionInInitializerError
    at com.mmh.epeius.server.javabase.MapStructTest.do2VoTest(MapStructTest.java:37)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:73)
    at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:83)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: Cannot find implementation for com.mmh.epeius.server.javabase.mapstruct.UserConverter
    at org.mapstruct.factory.Mappers.getMapper(Mappers.java:79)
    at com.mmh.epeius.server.javabase.mapstruct.UserConverter.<clinit>(UserConverter.java:16)
    ... 31 more
Caused by: java.lang.ClassNotFoundException: Cannot find implementation for com.mmh.epeius.server.javabase.mapstruct.UserConverter
    at org.mapstruct.factory.Mappers.getMapper(Mappers.java:93)
    at org.mapstruct.factory.Mappers.getMapper(Mappers.java:76)
    ... 32 more
说是我们刚才写的映射接口找不到实现类，原因是我们少包了，在原来的基础上，在加上如下依赖
   <dependency>
            <groupId>org.mapstruct</groupId>
            <artifactId>mapstruct-processor</artifactId>
            <version>1.2.0.Final</version>
        </dependency>
再次运行，可以看到，没问题了
User(id=1, username=zhangsan, password=abc123, sex=1, birthday=1999-09-27, createTime=2021-06-27T14:46:58.680, config=[{"field1":"Test Field1","field2":500}])
UserVo(id=1, username=zhangsan, password=abc123, gender=1, birthday=1999-09-27, createTime=2021-06-27 14:46:58, config=[UserVo.UserConfig(field1=Test Field1, field2=500)])
示例代码参考：https://www.pdai.tech/md/develop/package/dev-package-x-mapstruct.html