Inject a Map defined in a properties file

[Nick.Stolwijk]

I want to inject a Map from a property file into my Bean. What is the best way to configure that?

My props:

a.b.c.1=foo
a.b.c.2=bar

Inside my bean I want a Map with the pairs (1, foo) (2, foo).

I have found a post on stackoverflow.com which stated:

- implement ApplicationContextAware and set the ApplicationContext as a field in your bean.
- in a @PostConstruct method call context.getBean("${aaa.props}")
- parse the result manually and set it to the desired fields

Only it seems that

context.getBean("${a.b.c.1}");

doesn't resolve to my property.

I also tried to add a property which was:
a.b.c.list=1,2,3
but I can't get those properties from the context.

Is there a way to solve this?

[zakhrim]

Maybe it's a silly question, but just to be sure, did you add the line

<context:property-placeholder location="classpath:/META-INF/....." />

to your app config?

Regards,
Stefano

[Nick.Stolwijk]

Maybe it's a silly question, but just to be sure, did you add the line

<context:property-placeholder location="classpath:/META-INF/....." />

to your app config?

Regards,
Stefano

Yes, I added the property-placeholder, other properties were being resolved.

My current solution is:

/**
 * Allows for making a Map from a properties file from a classpath location available in a bean factory. Can be used to
 * populate any bean property of type Map via a bean reference.
 * 
 * <p>
 * Supports loading from a properties file and/or setting local properties on this FactoryBean. The created Properties
 * instance will be merged from loaded and local values. If neither a location nor local properties are set, an
 * exception will be thrown on initialization.
 * 
 * @see #setLocation
 * @see #setProperties
 * @see #setLocalOverride
 * @see java.util.Properties
 */
public class MapFactoryBean extends PropertiesLoaderSupport implements FactoryBean<Map<String, String>> {

    private static final Logger LOG = LoggerFactory.getLogger(MapFactoryBean.class);
    private String mapPropertyName;

    @Override
    public Map<String, String> getObject() throws IOException {
        Properties props = mergeProperties();
        Map<String, String> map = Maps.newHashMap();
        boolean valid = true;

        String keyList = props.getProperty(mapPropertyName + ".list");
        if (StringUtils.isEmpty(keyList)) {
            LOG.error("Failed to read map '{}', missing list property.", mapPropertyName);
            valid = false;
        } else {
            valid = createMap(props, map, keyList);
        }
        if (valid) {
            return map;
        } else {
            throw new IllegalStateException("Failed to read map '" + mapPropertyName + "'.");
        }
    }

    private boolean createMap(final Properties props, final Map<String, String> map, final String keyList) {
        boolean valid = true;
        String[] keys = StringUtils.split(keyList, ",");
        for (String key : keys) {
            String value = props.getProperty(mapPropertyName + "." + key);
            if (value == null) {
                LOG.error("Failed to read map '{}': Missing value for key '{}'", mapPropertyName, key);
                valid = false;
            } else {
                map.put(key, value);
            }
        }
        return valid;
    }

    @Override
    public Class<?> getObjectType() {
        return Map.class;
    }

    @Override
    public boolean isSingleton() {
        return true;
    }

    /**
     * @param mapPropertyName
     *            the mapPropertyName to set
     */
    public void setMapPropertyName(final String mapPropertyName) {
        this.mapPropertyName = mapPropertyName;
    }
}

And configure it like this:

    <bean id="sampleBean" class="com.example.SampleBeanl">
        <property name="mapName">
            <bean class="com.example.spring.MapFactoryBean">
                <property name="location" value="classpath:example.properties" />
                <property name="mapPropertyName" value="com.example.map" />
            </bean>
        </property>
    </bean>

And this works. (And I now see I won't need the list property, I could just iterate over all the properties and only pick the ones starting with the mapPropertyName.)

[objectamit]

Spring doesn't have any in-built support for use-cases like this and your solution seems fine if its working correctly as per expectations in your code-base.