This article supplements the @Qualifier annotation in the IoC annotation commonly used in Spring .
When an object has multiple implementation classes, you can use the @Qualifier annotation to choose to use.
Example ( based on @PropertySource annotation in Spring ):
JdbcConfig class:
package config;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import org.apache.commons.dbutils.QueryRunner;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Scope;
import javax.sql.DataSource;
//和spring连接数据库相关的配置类
@Configuration
public class JdbcConfig {
@Value("${jdbc.driver}")
private String driver;
@Value("${jdbc.url}")
private String url;
@Value("${jdbc.username}")
private String username;
@Value("${jdbc.password}")
private String password;
//用于创建一个QueryRunner对象
@Bean(name = "runner")
@Scope(value = "prototype")
public QueryRunner createQueryRunner(@Qualifier(value = "dataSource1") DataSource dataSource) {
return new QueryRunner(dataSource);
}
//创建数据源对象
@Bean(name = "dataSource")
public DataSource createDataSource() {
try {
ComboPooledDataSource ds = new ComboPooledDataSource();
ds.setDriverClass(driver);
ds.setJdbcUrl(url);
ds.setUser(username);
ds.setPassword(password);
return ds;
} catch (Exception e) {
throw new RuntimeException(e);
}
}
//创建数据源对象
@Bean(name = "dataSource1")
public DataSource createDataSource1() {
try {
ComboPooledDataSource ds = new ComboPooledDataSource();
ds.setDriverClass(driver);
ds.setJdbcUrl("jdbc:mysql://localhost:3306/springtest02?serverTimezone=UTC");
ds.setUser(username);
ds.setPassword(password);
return ds;
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}