@Qualifier 不起作用

Question

我有 3 个数据源，我设置如下：

@Configuration
@Component
public class DataSourceConfig {

    @Bean("foo")
    @ConfigurationProperties(prefix = "spring.datasource.foo")
    public DataSource foo() {
        DataSource dataSource = DataSourceBuilder.create().build();
        return dataSource;
    }

    @Bean("bar")
    @ConfigurationProperties(prefix = "spring.datasource.bar")
    public DataSource bar() {
        DataSource dataSource = DataSourceBuilder.create().build();
        return dataSource;
    }

    @Bean("baz")
    @ConfigurationProperties(prefix = "spring.datasource.baz")
    public DataSource baz() {
        DataSource dataSource = DataSourceBuilder.create().build();
        return dataSource;
    }

}

我正在尝试将它们自动连接到我的消费者类中，如下所示：

import javax.sql.DataSource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Component;

@Component
public class MyClass {

    @Autowired
    public MyClass(
            @Autowired @Qualifier("foo") DataSource foo,
            @Autowired @Qualifier("bar") DataSource bar,
            @Autowired @Qualifier("baz") DataSource baz
            ) {
        ;
    }

}

当应用程序尝试启动时，我收到错误：

***************************
APPLICATION FAILED TO START
***************************

Description:

Parameter 0 of constructor in com.example.mypackage.MyClass required a single bean, but 3 were found:
    - foo: defined by method 'foo' in class path resource [com/example/DataSourceConfig.class]
    - bar: defined by method 'bar' in class path resource [com/example/DataSourceConfig.class]
    - baz: defined by method 'baz' in class path resource [com/example/DataSourceConfig.class] 

为什么@Qualifier 不起作用？

我正在使用 Spring Boot 1.5.6.RELEASE

Answer 1

此解决方案解决了有问题的问题，但它不能呈现完整的工作配置。

1. 设置主数据库。
2. 更改构造函数格式。

MyClass.java

@Component
public class MyClass {

    private final DataSource foo;
    private final DataSource bar;
    private final DataSource baz;

    @Autowired
    public MyClass(@Qualifier("foo") DataSource foo,
                   @Qualifier("bar") DataSource bar,
                   @Qualifier("baz") DataSource baz) {

        this.foo = foo;
        this.bar = bar;
        this.baz = baz;

    }

}

DataSourceConfig.java

@Configuration
@Component
public class DataSourceConfig {

    @Primary
    @Bean("foo")
    @ConfigurationProperties(prefix = "spring.datasource.foo")
    public DataSource foo() {
        DataSource dataSource = DataSourceBuilder.create().build();
        return dataSource;
    }

    @Bean("bar")
    @ConfigurationProperties(prefix = "spring.datasource.bar")
    public DataSource bar() {
        DataSource dataSource = DataSourceBuilder.create().build();
        return dataSource;
    }

    @Bean("baz")
    @ConfigurationProperties(prefix = "spring.datasource.baz")
    public DataSource baz() {
        DataSource dataSource = DataSourceBuilder.create().build();
        return dataSource;
    }

}

这会留下错误org.hibernate.HibernateException: Access to DialectResolutionInfo cannot be null when 'hibernate.dialect' not set。为此，我建议关注this question，因为它关注问题的主题，而这个问题围绕@Bean 名称并使用@Qualifier 引用它们。

Answer 2

试试这个：

import javax.sql.DataSource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Component;

    @Component
    public class MyClass {

    private DataSource foo;
    private DataSource bar; 
    private DataSource baz;

    @Autowired
    public MyClass(
            @Qualifier("foo") final DataSource foo,
            @Qualifier("bar") final DataSource bar,
            @Qualifier("baz") final DataSource baz
            ) {
        ;
    }

}

Answer 3

通过添加 @Primary 注释使其中一个 bean 成为主要的。然后应该识别限定符。