我遇到了一个我不知道如何解决的问题。我使用Spring Boot创建了Restful API，并且正在实现DTO-Domain-Entity模式，因此在这种特殊情况下，我具有此 Controller 的方法
@RequestMapping(method = RequestMethod.POST)
@ResponseBody
public ResponseEntity<UserResponseDTO> createUser(@RequestBody UserRequestDTO data) {
UserDomain user = this.mapper.map(data, UserDomain.class);
UserDomain createdUser = this.service.createUser(user);
UserResponseDTO createdUserDTO = this.mapper.map(createdUser, UserResponseDTO.class);
return new ResponseEntity<UserResponseDTO>(createdUserDTO, HttpStatus.CREATED);
}
public class UserDomain {
private Long id;
private Date createdDate;
private Date updatedDate;
private String username;
private String password;
@Value("${default.user.enabled:true}") // I have default-values.properties being loaded in another configuration file
private Boolean enabled;
}
我正在将UserRequestDTO对象转换为UserDomain。据我了解，UserRequestDTO是正在注入(inject)的bean。然后我将其转换为UserDomain，这里的问题是UserDomain对象不是组件，因此enabled属性将不采用默认值。
如果我不想将UserDomain当作bean处理，我该如何使spring加载默认值(在这种情况下只是启用属性)？
编辑
答案不一样，因为我的目标是使用@Value批注完成它。
无论如何，这样做会是康斯坦丁建议的更好的方法吗？
public class UserDomain {
@Autowired
private Environment environment;
private Boolean enabled;
UserDomain(){
this.enabled = environment.getProperty("default.user.enabled");
// and all the other ones
}
}
最佳答案
如果您的映射器有一个采用已经准备好的实例的方法，而不是Class，那么您可以添加原型(prototype)作用域的UserDomain bean并从 Controller 方法中调用context.getBean()。
Controller
...
@Autowired
private WebApplicationContext context;
@RequestMapping(method = RequestMethod.POST)
@ResponseBody
public ResponseEntity<UserResponseDTO> createUser(@RequestBody UserRequestDTO data) {
UserDomain user = this.mapper.map(data, getUserDomain());
UserDomain createdUser = this.service.createUser(user);
UserResponseDTO createdUserDTO = this.mapper.map(createdUser, UserResponseDTO.class);
return new ResponseEntity<UserResponseDTO>(createdUserDTO, HttpStatus.CREATED);
}
private UserDomain getUserDomain() {
return context.getBean(UserDomain.class);
}
...
Spring 配置
@Configuration
public class Config {
@Bean
public static PropertySourcesPlaceholderConfigurer properties() {
PropertySourcesPlaceholderConfigurer propConfigurer = new PropertySourcesPlaceholderConfigurer();
propConfigurer.setLocation(new ClassPathResource("application.properties"));
return propConfigurer;
}
@Bean
@Scope("prototype")
public UserDomain userDomain() {
return new UserDomain();
}
...
}
否则，您可以使用
@Configurable 和AspectJ编译时编织。但是，您必须决定是否值得在您的项目中引入编织，因为您还有其他方法可以处理这种情况。pom.xml
...
<!-- additional dependencies -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aspects</artifactId>
<version>4.2.0.RELEASE</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>1.8.6</version>
</dependency>
...
<!-- enable compile-time weaving with aspectj-maven-plugin -->
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>aspectj-maven-plugin</artifactId>
<version>1.7</version>
<configuration>
<complianceLevel>1.8</complianceLevel>
<encoding>UTF-8</encoding>
<aspectLibraries>
<aspectLibrary>
<groupId>org.springframework</groupId>
<artifactId>spring-aspects</artifactId>
</aspectLibrary>
</aspectLibraries>
<Xlint>warning</Xlint>
</configuration>
<executions>
<execution>
<goals>
<goal>compile</goal>
<goal>test-compile</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
...
UserDomain.java
@Configurable
public class UserDomain {
private Long id;
private Date createdDate;
private Date updatedDate;
private String username;
private String password;
@Value("${default.user.enabled:true}")
private Boolean enabled;
...
}
Spring 配置
@EnableSpringConfigured与
<context:spring-configured>相同。@Configuration
@EnableSpringConfigured
public class Config {
@Bean
public static PropertySourcesPlaceholderConfigurer properties() {
PropertySourcesPlaceholderConfigurer propConfigurer = new PropertySourcesPlaceholderConfigurer();
propConfigurer.setLocation(new ClassPathResource("application.properties"));
return propConfigurer;
}
...
}
请引用Spring文档以获取有关AspectJ and @Configurable的更多信息。
编辑
关于您的编辑。
请注意，您在此处使用
@Autowired 。这意味着UserDomain实例必须由Spring容器进行管理。容器不知道在其外部创建的实例，因此 @Autowired (确切地说是 @Value )将无法解析此类实例，例如UserDomain userDomain = new UserDomain()或UserDomain.class.newInstance()。因此，您仍然必须在上下文中添加原型(prototype)作用域的UserDomain bean。实际上，这意味着建议的方法与 @Value 相关的方法类似，不同之处在于它将UserDomain与Spring Environment 相关联。因此，这是不好的。仍然可以使用
Environment 和 ApplicationContextAware 设计更好的解决方案，而无需将域对象绑定(bind)到Spring。ApplicationContextProvider.java
public class ApplicationContextProvider implements ApplicationContextAware {
private static ApplicationContext applicationContext;
public static <T> T getEnvironmentProperty(String key, Class<T> targetClass, T defaultValue) {
if (key == null || targetClass == null) {
throw new NullPointerException();
}
T value = null;
if (applicationContext != null) {
System.out.println(applicationContext.getEnvironment().getProperty(key));
value = applicationContext.getEnvironment().getProperty(key, targetClass, defaultValue);
}
return value;
}
public void setApplicationContext(ApplicationContext applicationContext) {
this.applicationContext = applicationContext;
}
}
UserDomain.java
public class UserDomain {
private Boolean enabled;
public UserDomain() {
this.enabled = ApplicationContextProvider.getEnvironmentProperty("default.user.enabled", Boolean.class, false);
}
...
}
Spring 配置
@Configuration
@PropertySource("classpath:application.properties")
public class Config {
@Bean
public ApplicationContextProvider applicationContextProvider() {
return new ApplicationContextProvider();
}
...
}
但是，我不喜欢这种方法的额外复杂性和草率性。我认为这根本没有道理。