java - Spring :如何通过从外部属性文件读取来使用@Value注释注入(inject)值？

我有以下情况
-具有MongoService类，该类从文件读取主机，端口，数据库

xml配置

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations">
            <list>
                <value>file:///storage/local.properties</value>
            </list>
        </property>
    </bean>
</beans>

local.properties 看起来像

### === MongoDB interaction === ###
host="127.0.0.1"
port=27017
database=contract

和 MongoService类作为

@Service
public class MongoService {

    private final Mongo mongo;
    private final String database;
    private static final Logger LOGGER = LoggerFactory.getLogger(MongoService.class);

    public MongoService(@Nonnull final @Value("#{ systemProperties['host']}") String host, @Nonnull final @Value("#{ systemProperties['port']}") int port, @Nonnull final @Value("#{ systemProperties['database']}") String db) throws UnknownHostException {
        LOGGER.info("host=" + host + ", port=" + port + ", database=" + db);
        mongo = new Mongo(host, port);
        database = db;
    }
}

当我想测试bean是否可以用时，我在
MongoServiceTest.java

public class MongoServiceTest {

    @Autowired
    private MongoService mongoService;

}

它抱怨说can not identify bean for MongoService。

然后我将以下内容添加到上面的xml中

<bean id="mongoService" class="com.business.persist.MongoService"></bean>

然后它抱怨说"No Matching Constructor found"
我想做什么

a。)MongoService应该是@Autowired并从<value>file:///storage/local.properties</value>读取配置参数

问题

a。)在构造函数中访问值是否正确？ (file name is local.properties and I am using @Value("#{ systemProperties['host']}") syntax)
b。)我需要做些什么，以便@Autowired private MongoService mongoService正确加载并从local.properties文件中读取值。

附言我是Spring的新手，真的不知道该如何做

非常感谢您的帮助

最佳答案

我认为，您必须按如下所示向构造xml添加构造函数-arg。

<bean id="mongoService" class="com.business.persist.MongoService">

        <constructor-arg type="java.lang.String">
            <value>host</value>
        </constructor-arg>

        <constructor-arg type="int">
            <value>port</value>
        </constructor-arg>

        <constructor-arg type="java.lang.String">
            <value>database</value>
        </constructor-arg>

    </bean>

我不确定，最好的方法可能是添加基于Java的Bean配置。从xml中删除bean定义，并添加基于Java的congfig，如下所示

@Service
public class MongoService {

    private final Mongo mongo;
    private final String database;
    private static final Logger LOGGER = LoggerFactory.getLogger(MongoService.class);

@bean
    public MongoService(@Nonnull final @Value("#{ systemProperties['host']}") String host, @Nonnull final @Value("#{ systemProperties['port']}") int port, @Nonnull final @Value("#{ systemProperties['database']}") String db) throws UnknownHostException {
        LOGGER.info("host=" + host + ", port=" + port + ", database=" + db);
        mongo = new Mongo(host, port);
        database = db;
    }
}

高温超导