在Java Spring中将一个bean的值设置为另一个bean

Question

我在Spring bean配置中遇到两个主要问题：1.当我从应用程序上下文中检索bean时，通过属性文件读取的属性没有保留。 2.我在弄清楚如何将一个bean的值设置为另一个bean时遇到麻烦-在下面的示例中，我试图将Plan bean的Metric属性设置为某个bean。

我有两个小类，一个度量标准和一个较大的计划：

@Component
public class Metric {

   @Value("${nameOfMetric}")
   String name;

   @Value("${empID}")
   String empID;

   @Value("${value:0.0}")
   Double value;
   }

还有一个较大的Plan对象，它具有三个不同的Metrics作为属性：

public class Plan {

public Metric hoursWorked;

public Metric monthlyDeals;

public Metric monthlyGoal;
...}

我还有一个要读取的属性文件：

nameOfMetric = Untitled Metric
empID = Unknown
hoursWorked = 120.0
monthlyDeals = 40.0
monthlyGoal = 100.0

我有办法为每个指标（hoursWorked，monthlyDeals，monthlyGoal）创建bean，然后将每个bean注入Plan bean吗？ 到目前为止，我尝试使用带有@Configuration批注的PropertyConfig类：

@Inject
private Environment environment;

private Metric injectMetric(String propertyName){

    Metric metric = new Metric();
    metric.setEmpID(environment.getProperty("empID"));
    metric.setName(propertyName);
    metric.setValue(Double.parseDouble(environment.getProperty(propertyName)));
    System.out.println("Metric injected: " + metric.toString());
    return metric;
}

@Bean
public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
    return new PropertySourcesPlaceholderConfigurer();
}

@Bean(name = {"hoursWorkedBean"})
@Scope("prototype")
public Metric hoursWorked() {
    Metric metric = injectMetric("hoursWorked");
    return metric;
}

但是，当我尝试访问此bean时，我在主应用程序中获得了默认值或null值，表明这些属性尚未持久：

    Metric hoursWorked = (Metric) ctx.getBean("hoursWorkedBean");

    System.out.println(hoursWorked.getName()); // prints out "Untitled Metric", but should print out "hoursWorked"

Answer 1

您需要自动连接指标

public class Plan {

@Autowired   
public Metric hoursWorked;

@Autowired
public Metric monthlyDeals;

@Autowired
public Metric monthlyGoal;
...}

Answer 2

您可以在Spring Boot应用程序中使用@ConfigurationProperties。

您可以在Spring Boot应用程序中进行以下配置：

资源/application.yml

metrics:
  hoursWorked:
    name: one
    empID: 1
    value: 1.23
  monthlyDeals:
    name: two
    empID: 2
    value: 2.34
  monthlyGoal:
    name: three
    empID: 3
    value: 3.45

Metric.java （不要忘记getter / setter）

public class Metric {
    private String name;
    private String empID;
    private Double value;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmpID() {
        return empID;
    }

    public void setEmpID(String empID) {
        this.empID = empID;
    }

    public Double getValue() {
        return value;
    }

    public void setValue(Double value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return "Metric{" +
                "name='" + name + '\'' +
                ", empID='" + empID + '\'' +
                ", value=" + value +
                '}';
    }
}

Metrics.java （定义度量标准名称/限定词/配置）

public class Metrics {

    public static final String HOURS_WORKED = "hoursWorked";
    public static final String MONTHLY_DEALS = "monthlyDeals";
    public static final String MONTHLY_GOAL = "monthlyGoal";
}

MetricsConfiguration.java （创建bean并通过配置对其进行初始化）

@Configuration
public class MetricsConfiguration {

    @Bean
    @Scope(BeanDefinition.SCOPE_PROTOTYPE)
    @Qualifier(Metrics.HOURS_WORKED)
    @ConfigurationProperties(prefix = "metrics." + Metrics.HOURS_WORKED)
    public Metric hoursWorked() {
        return new Metric();
    }

    @Bean
    @Scope(BeanDefinition.SCOPE_PROTOTYPE)
    @Qualifier(Metrics.MONTHLY_DEALS)
    @ConfigurationProperties("metrics." + Metrics.MONTHLY_DEALS)
    public Metric monthlyDeals() {
        return new Metric();
    }

    @Bean
    @Scope(BeanDefinition.SCOPE_PROTOTYPE)
    @Qualifier(Metrics.MONTHLY_GOAL)
    @ConfigurationProperties("metrics." + Metrics.MONTHLY_GOAL)
    public Metric monthlyGoal() {
        return new Metric();
    }
}

DemoRunner.java （用于测试代码的命令行运行器）

@Component
public class DemoRunner implements CommandLineRunner
{
    @Autowired
    private List<Metric> allMetrics;

    @Autowired
    @Qualifier(Metrics.HOURS_WORKED)
    private Metric hoursWorkedMetric;

    @Autowired
    @Qualifier(Metrics.MONTHLY_DEALS)
    private Metric monthlyDealsMetric;

    @Autowired
    @Qualifier(Metrics.MONTHLY_GOAL)
    private Metric monthlyGoalMetric;

    @Override
    public void run(String... args) throws Exception {
        System.out.println();

        System.out.println("All metrics:");
        allMetrics.stream().forEach(System.out::println);

        System.out.println();
        System.out.println("HOURS_WORKED metric: " + hoursWorkedMetric);
        System.out.println("MONTHLY_DEALS metric: " + monthlyDealsMetric);
        System.out.println("MONTHLY_GOAL metric: " + monthlyGoalMetric);

        System.out.println();
    }
}

DemoApplication.java （SpringBoot应用程序初始化）

@SpringBootApplication
public class DemoApplication {

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