复杂对象的注入

1. 书写Component类

• Component类就是你希望被注入的Java类

public class JDBC {
    
    public final DataSource dataSource;

    @Autowired
    public JDBC(DataSource dataSource){
        this.dataSource = dataSource;
    }
}

• 优先将@Autowired注解写在构造器函数上，因为类加载器优先使用构造器为成员变量赋值，其次才为@Autowired变量注入值。

2. 书写YML注入文件

• 在这个文件中，为所要注入的变量赋值

spring:
  datasource:
    username: root
    password: 6158
    url: jdbc:mysql://localhost:3307/users?useUnicode=true&characterEncoding=UTF-8&useSSL=false&serverTimezone=Asia/Shanghai&zeroDateTimeBehavior=CONVERT_TO_NULL&allowPublicKeyRetrieval=true
    driver-class-name: com.mysql.cj.jdbc.Driver
    type: com.alibaba.druid.pool.DruidDataSource
    initialSize: 5
    minIdle: 5
    maxActive: 20
    maxWait: 60000
    timeBetweenEvictionRunsMillis: 60000
    minEvictableIdleTimeMillis: 300000
    validationQuery: SELECT 1 FROM DUAL
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    poolPreparedStatements: true
    filters: stat,wall
    maxPoolPreparedStatementPerConnectionSize: 20
    useGlobalDataSourceStat: true
    connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500

3. 为Component类添加注解

@Component
@ConfigurationProperties(prefix = "spring.datasource")
public class JDBC {
    
    public final DataSource dataSource;

    @Autowired
    public JDBC(DataSource dataSource){
        this.dataSource = dataSource;
    }
}

4. 在Controller中调用Component类并添加注解

@Controller
public class MyController {
    @Autowired
    private JDBC jdbc;
    
    @PostMapping(value = "/user/login")
    public String login(){
        //就可以使用已注入的JDBC对象了
        return "redirect:/main";
    }
}

写在最后

@Autowired注解底层实现了单例模式，即多次注入的不同引用，会得到同一个对象

@Autowired
JDBC jdbc1;

@Autowired
JDBC jdbc2;

System.out.println(jdbc1 == jdbc2);

上述程序输入true

复杂对象的注入

原文：https://www.cnblogs.com/seek-wind/p/13206416.html