bean属性注入的4种方式

以数据库连接为例，测试bean属性注入的几种方式
1.@Autowired注入
2.构造方法注入
3.@Bean方法形参注入
4.直接在@Bean方法上使用@ConfigurationProperties(prefix=“jdbc”)

JdbcProperties文件：
jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/xxx
jdbc.username=root
jdbc.password=xxx

@Configuration//声明一个类是一个java配置类， 相当于xml配置文件
@EnableConfigurationProperties(JdbcProperties.class)
public class JdbcConfiguration {
    @Autowired
    private JdbcProperties jdbcProperties;
    @Value("${jdbc.driverClassName}")
    private String driverClassName;
    @Value("${jdbc.url}")
    private String url;
    @Value("${jdbc.username}")
    private String username;
    @Value("${jdbc.password}")
    private String password;
       @Bean//把方法的返回值注入到spring 容器
    public DataSource dataSource() {
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(this.driverClassName);
        dataSource.setUrl(this.url);
        dataSource.setUsername(this.username);
        dataSource.setPassword(this.password);
        return dataSource;
    }

application.properties:
jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/leyou
jdbc.username=root
jdbc.password=123

构造方法注入

@Configuration//声明一个类是一个java配置类， 相当于一个xml配置文件
@EnableConfigurationProperties(JdbcProperties.class)
public class JdbcConfiguration {
    //  @Autowired
    private JdbcProperties jdbcProperties;

    public JdbcConfiguration(JdbcProperties jdbcProperties) {
        this.jdbcProperties = jdbcProperties;
    }

    @Bean//把方法的返回值注入到spring 容器
    public DataSource dataSource() {
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(this.jdbcProperties.getDriverClassName());
        dataSource.setUrl(this.jdbcProperties.getUrl());
        dataSource.setUsername(this.jdbcProperties.getUsername());
        dataSource.setPassword(this.jdbcProperties.getPassword());
        return dataSource;
    }
}

set方式注入

@ConfigurationProperties(prefix = "jdbc" )
public class JdbcProperties {

    private String driverClassName;
    private String url;
    private String username;
    private String password;

    public String getDriverClassName() {
        return driverClassName;
    }

    public void setDriverClassName(String driverClassName) {
        this.driverClassName = driverClassName;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

@Configuration//声明一个类是一个java配置类， 相当于一个xml配置文件
@EnableConfigurationProperties(JdbcProperties.class)
public class JdbcConfiguration {
    @Autowired
    private JdbcProperties jdbcProperties;

    

    @Bean//把方法的返回值注入到spring 容器
    public DataSource dataSource() {
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(this.jdbcProperties.getDriverClassName());
        dataSource.setUrl(this.jdbcProperties.getUrl());
        dataSource.setUsername(this.jdbcProperties.getUsername());
        dataSource.setPassword(this.jdbcProperties.getPassword());
        return dataSource;
    }
}

传参注入

@Configuration//声明一个类是一个java配置类， 相当于一个xml配置文件
@EnableConfigurationProperties(JdbcProperties.class)
public class JdbcConfiguration {
//    @Autowired
//    private JdbcProperties jdbcProperties;
//
//    public JdbcConfiguration(JdbcProperties jdbcProperties) {
//        this.jdbcProperties = jdbcProperties;
//    }

    @Bean//把方法的返回值注入到spring 容器
    public DataSource dataSource(JdbcProperties jdbcProperties) {
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName( jdbcProperties.getDriverClassName());
        dataSource.setUrl( jdbcProperties.getUrl());
        dataSource.setUsername( jdbcProperties.getUsername());
        dataSource.setPassword( jdbcProperties.getPassword());
        return dataSource;
    }
}

最简介的方式：要保证返回值有相应的set和get方法，并且配置文件的名称要和返回值属性名称相同

@Configuration//声明一个类是一个java配置类， 相当于一个xml配置文件
@EnableConfigurationProperties(JdbcProperties.class)
public class JdbcConfiguration {
//    @Autowired
//    private JdbcProperties jdbcProperties;
//
//    public JdbcConfiguration(JdbcProperties jdbcProperties) {
//        this.jdbcProperties = jdbcProperties;
//    }

    @Bean//把方法的返回值注入到spring 容器
    @ConfigurationProperties(prefix = "jdbc")
    public DataSource dataSource(JdbcProperties jdbcProperties) {
        DruidDataSource dataSource = new DruidDataSource();
        return dataSource;
    }
}

本文地址：https://blog.csdn.net/qq_40971668/article/details/110260733