Spring常用注解-@Value @ConfigurationProperties一、Spring工程二、SpringBoot工程2.1、配置文件文件三、总结

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我是靠谱客的博主独特月饼，最近开发中收集的这篇文章主要介绍Spring常用注解-@Value @ConfigurationProperties一、Spring工程二、SpringBoot工程2.1、配置文件文件三、总结，觉得挺不错的，现在分享给大家，希望可以做个参考。

之前有错误的认识，@Value只能注入基本数据类型，但是其实是错误的，总结一下@Value特点：

1）@Value所有数据类型它都可以注入。

2）@Value注入不依赖set方法，@Autowired也不需要

一、Spring工程

建立Spring工程，不要使用Springboot

1.1、application.properties文件

username=mysql-root
clusterArray=shanghai,beijing,shenzhen
clusterList=hangzhou,guangzhou
clusterList2=tianjin_wuhan_fuzhou
cluster.weight={"shanghai":"90","beijing":"87","shenzhen":"85","guangzhou":"100"}

last_access = 2021-10-08T14:11:30
created_date = 20211008

1.2、创建配置类

创建一个配置类，用于加载配置文件

@Configuration
@PropertySource(value = "classpath:application.properties")
public class AppConfig {
    @Bean
    public Data getData() {
        return new Data();
    }

    @Bean("accountService")
    public AccountService getAccountService() {
        return new AccountService();
    }
}

public class AccountService {
}

public class Data {
    @Value("${username}")
    private String uname;

    @Value("${clusterArray}")  //默认逗号分隔
    private String[] clusters;

    @Value("${clusterList}") //默认逗号分隔
    private List<String> clusterList;

    @Value("#{'${clusterList2}'.split('_')}") //按照_分隔, 注意|是特殊字符
    private List<String> clusterList2;

    @Value("#{${cluster.weight}}")
    private Map<String, String> weights;

    // 通过SpEL表达式注入
    @Value("#{T(java.time.LocalDateTime).parse('${last_access}')}")
    private LocalDateTime lastAccess;

    @Value("#{new java.text.SimpleDateFormat('yyyyMMdd').parse('${created_date}')}")
    private Date createdDate;

    // 通过SpEl表达式 注入其他bean对象
    @Value("#{accountService}")
    private AccountService service;

    public Data() {
    }

    @Override
    public String toString() {
        return "Data{" +
                "uname='" + uname + ''' +
                ", nclusters=" + Arrays.toString(clusters) +
                ", nclusterList=" + clusterList +
                ", nclusterList2=" + clusterList2 +
                ", nweights=" + weights +
                ", nlastAccess=" + lastAccess +
                ", ncreatedDate=" + createdDate +
                ", nservice=" + service +
                '}';
    }
}

//创建单元测试
public class MyTest {

    @Test
    public void test1() {
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
        Data data = applicationContext.getBean("getData", Data.class);
        System.out.println(data);
    }
}


/*
输出结果：
Data{uname='mysql-root', 
clusters=[shanghai, beijing, shenzhen], 
clusterList=[hangzhou,guangzhou], 
clusterList2=[tianjin, wuhan, fuzhou], 
weights={shanghai=90, beijing=87, shenzhen=85, guangzhou=100}, 
lastAccess=2021-10-08T14:11:30, 
createdDate=Fri Oct 08 00:00:00 CST 2021, 
service=com.example.service.AccountService@1e66f1f5}

*/

由此可见对于比较复杂类型，我们需要借助SpEl表达式才能实现注入，到了Springboot就比较简单了，下面是SpringBoot做法。

二、SpringBoot工程

SpringBoot默认支持两种配置文件，properties（优先级高）和yml文件，使用哪种都可以

2.1、配置文件文件

application.properties配置文件，注意时间格式，不需要加双引号

app.username=mysql-root
app.clusterArray=shanghai,beijing,shenzhen
app.clusterList=hangzhou,guangzhou
app.cluster.weight={"shanghai":"90","beijing":"87","shenzhen":"85","guangzhou":"100"}

app.last_access = 2021-10-08 14:11:30
app.created_date = 20211008

server.port=9001

application.yml，时间戳需要加双引号

app:
  username: mysql-root
  clusterArray:
    - shanghai
    - beijing
    - shenzhen
  clusterList:
    - hangzhou
    - guangzhou
  cluster:
    weight:
      shanghai: 90
      beijing: 87
      shenzhen: 85
      guangzhou: 100
  last_access: "2021-10-08 14:11:30"
  created_date: "20211008"

server:
  port: 9001


@Component
@ConfigurationProperties(prefix = "app")
public class Data {
    private String userName;

    private String[] clusterArray;

    private List<String> clusterList;

    private Cluster cluster;

    @DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private LocalDateTime lastAccess;

    @DateTimeFormat(pattern = "yyyyMMdd")
    private Date createdDate;

    // 通过SpEl表达式 注入其他bean对象, 这里用@Autowired也可以
    @Value("#{accountService}")
    private AccountService service;

    public Data() {
    }


    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String[] getClusterArray() {
        return clusterArray;
    }

    public void setClusterArray(String[] clusterArray) {
        this.clusterArray = clusterArray;
    }

    public List<String> getClusterList() {
        return clusterList;
    }

    public void setClusterList(List<String> clusterList) {
        this.clusterList = clusterList;
    }

    public Cluster getCluster() {
        return cluster;
    }

    public void setCluster(Cluster cluster) {
        this.cluster = cluster;
    }

    public LocalDateTime getLastAccess() {
        return lastAccess;
    }

    public void setLastAccess(LocalDateTime lastAccess) {
        this.lastAccess = lastAccess;
    }

    public Date getCreatedDate() {
        return createdDate;
    }

    public void setCreatedDate(Date createdDate) {
        this.createdDate = createdDate;
    }

    @Override
    public String toString() {
        return "Data{" +
                "userName='" + userName + ''' +
                ", clusterArray=" + Arrays.toString(clusterArray) +
                ", clusterList=" + clusterList +
                ", cluster=" + cluster +
                ", lastAccess=" + lastAccess +
                ", createdDate=" + createdDate +
                ", service=" + service +
                '}';
    }
}

通过springboot工程，只需要使用@ConfigurationProperties注解，就可以注入大部分数据。有两点需要说明：

1）@ConfigurationProperties注解的类，需要有set方法，才能注入数据

2）@ConfigurationProperties中prefix不是必须的，如果不写idea会显示波浪线（可以忽略）