java - 带有 Java 可选 getter 的 REST 响应对象

Question

我正在 Spring Boot 中编写 REST 服务。我想让 DTO 类的一些字段作为可选 getter 进行访问。这是示例。

@JsonInclude(Include.NON_NULL)
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, property = "profileType", visible = true, defaultImpl = InvalidUserDTO.class)
@JsonSubTypes({ @JsonSubTypes.Type(value = ClientDTO.class, name = "CLIENT"), @JsonSubTypes.Type(value = DriverDTO.class, name = "DRIVER") })
public abstract class UserDTO {

    private String password;

    private Optional<String> email;

通过这种方法，在我的 REST 响应中，我得到类似 email: {"present": true} 的内容，而不是电子邮件的实际值。

为了解决这个问题，我尝试将 Jdk8Module 依赖项添加到类路径中。

但是，当尝试在使用可选的端点上调用我的服务时，这只会导致以下错误:

    {"message":"Internal Server Error","details":"Handler dispatch failed; nested exception is java.lang.AbstractMethodError: 

com.fasterxml.jackson.databind.ser.std.ReferenceTypeSerializer.withResolved(Lcom/fasterxml/jackson/databind/BeanProperty;Lcom/fasterxml/jackson/databind/jsontype/TypeSerializer;
Lcom/fasterxml/jackson/databind/JsonSerializer;Lcom/fasterxml/jackson/databind/util/NameTransformer;Lcom/fasterxml/jackson/annotation/JsonInclude$Include;)
Lcom/fasterxml/jackson/databind/ser/std/ReferenceTypeSerializer;"}

我有什么遗漏的吗？为什么会发生这种情况？

这是 ObjectMapper 配置:

@SpringBootApplication
public class MainApplication extends SpringBootServletInitializer {

    @Autowired
    void configureObjectMapper(final ObjectMapper mapper) {
        mapper
            .registerModule(new ParameterNamesModule())
            .registerModule(new Jdk8Module());
    }    

    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        servletContext.setInitParameter("webAppRootKey", "newfacesBackend.root");
        servletContext.setInitParameter("isLog4jAutoInitializationDisabled", "true");
        super.onStartup(servletContext);
    }

    public static void main(String[] args) throws Exception {
        SpringApplication.run(MainApplication.class, args);
    }

}

Gradle 依赖项:

buildscript {
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:1.5.4.RELEASE")
    }
}

apply plugin: 'com.github.ben-manes.versions'
apply plugin: 'maven-publish'
apply plugin: 'org.springframework.boot'


configurations {
    compile.exclude group:'ch.qos.logback'
}

dependencies {


    compile("org.springframework.boot:spring-boot-starter-actuator")
    compile("org.springframework.boot:spring-boot-starter-web")
    compile("com.fasterxml.jackson.datatype:jackson-datatype-jdk8:2.9.4")

    compile("com.fasterxml.jackson.module:jackson-module-parameter-names:2.9.4")

Answer 1

您应该使用映射器注册 JDK8 模块，如下所示:

ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new Jdk8Module());

或者，

您可以通过将以下内容添加到主 Spring Boot 应用程序类来全局执行此操作:

  @Autowired
  void configureObjectMapper(final ObjectMapper mapper) {
   mapper.registerModule(new ParameterNamesModule())
  .registerModule(new Jdk8Module());
  }

ParameterNamesModule 的依赖项是:

<dependency>
    <groupId>com.fasterxml.jackson.module</groupId>
    <artifactId>jackson-module-parameter-names</artifactId>
</dependency>