Spring XML配置中如何设置动态MongoDB Client URI（含认证）

方法一：使用SpEL表达式引用Spring Bean #

你当前XML里的{username}是属性文件占位符语法，要引用SecretImpl生成的username、password Bean，得改用SpEL表达式（#{...}语法），通过@beanName直接引用容器内的Bean：

修改XML配置：

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:mongo="http://www.springframework.org/schema/data/mongo"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
                           http://www.springframework.org/schema/beans/spring-beans.xsd
                           http://www.springframework.org/schema/data/mongo
                           http://www.springframework.org/schema/data/mongo/spring-mongo.xsd
                           http://www.springframework.org/schema/context
                           http://www.springframework.org/schema/context/spring-context.xsd">

    <!-- 扫描SecretImpl所在包，让Spring加载该配置类 -->
    <context:component-scan base-package="com.your.package.path" />

    <mongo:db-factory id="devMongoConnection"
                      client-uri="mongodb://#{@username}:#{@password}@server_1:27000,server_2:27000,server_3:27000/db_name?replicaSet=test" />
</beans>

同时修正SecretImpl的构造逻辑（Spring需要能无参实例化该配置类）：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class SecretImpl {

    private final Secret secret;

    // 在构造方法中调用内部API获取凭证
    public SecretImpl() {
        this.secret = Internal_API_For_Secrets();
    }

    @Bean(name="username")
    public String username() {
        return secret.getUsername();
    }

    @Bean(name="password")
    public String password() {
        return secret.getPassword();
    }
}

Spring启动时会先加载SecretImpl生成username、password Bean，再通过SpEL把值注入到MongoDB连接串中。

方法二：完全用Java配置生成MongoDbFactory #

如果不想混合XML与Java配置，直接用Java代码创建MongoDbFactory Bean会更灵活，彻底规避硬编码问题：

1. 修正MongoConstructor，通过构造注入获取Secret：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class MongoConstructor {

    private final Secret secret;
    private final String db = "db_name";
    private final String rs = "test";

    @Autowired
    public MongoConstructor(Secret secret) {
        this.secret = secret;
    }

    public String getMongoUri() {
        return String.format("mongodb://%s:%s@server_1:27000,server_2:27000,server_3:27000/%s?replicaSet=%s",
                secret.getUsername(),
                secret.getPassword(),
                db,
                rs);
    }
}

2. 编写MongoDB配置类生成MongoDbFactory：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
import com.mongodb.MongoClientURI;

@Configuration
@Import(SecretImpl.class) // 引入Secret配置类
public class MongoConfig {

    private final MongoConstructor mongoConstructor;

    @Autowired
    public MongoConfig(MongoConstructor mongoConstructor) {
        this.mongoConstructor = mongoConstructor;
    }

    @Bean(name = "devMongoConnection")
    public SimpleMongoDbFactory devMongoConnection() {
        MongoClientURI uri = new MongoClientURI(mongoConstructor.getMongoUri());
        return new SimpleMongoDbFactory(uri);
    }
}

3. 加载该Java配置类：如果用XML，添加<context:component-scan>扫描MongoConfig所在包；如果是Spring Boot，直接在启动类加@Import(MongoConfig.class)即可，无需保留XML中的<mongo:db-factory>配置。

内容的提问来源于stack exchange，提问作者SVill