Question

我想知道，如果有一种通用方法来填充带有属性的地图，您只需要知道前缀。

假设有很多属性，比如

namespace.prop1=value1
namespace.prop2=value2
namespace.iDontKnowThisNameAtCompileTime=anothervalue

我希望有一种通用的方法在地图中填充此属性，例如

@Component
@ConfigurationProperties("namespace")
public class MyGenericProps {
    private Map<String, String> propmap = new HashMap<String, String>();

    // setter and getter for propmap omitted

    public Set<String> returnAllKeys() {
        return propmap.keySet();
    }
}

或者是否有另一种方便的方法来收集具有特定前缀的所有属性，而不是迭代环境中的所有PropertySource？

由于 Hansjoerg

Answer 1

只要您乐意将每个属性添加到地图中，而不仅仅是您事先不知道的属性，您可以使用@ConfigurationProperties执行此操作。如果你想抓住namespace下面的所有内容，那么你需要使用一个空前缀并为名为namespace的地图提供一个getter：

@ConfigurationProperties("")
public class CustomProperties {

    private final Map<String, String> namespace = new HashMap<>();

    public Map<String, String> getNamespace() {
        return namespace;
    }

}

Spring Boot使用getNamespace方法检索地图，以便可以向其添加属性。有了这些属性：

namespace.a=alpha
namespace.b=bravo
namespace.c=charlie

namespace地图将包含三个条目：

{a=alpha, b=bravo, c=charlie}

如果属性嵌套得更深，例如：

namespace.foo.bar.a=alpha
namespace.foo.bar.b=bravo
namespace.foo.bar.c=charlie

然后您使用namespace.foo作为前缀，并分别在namespace上将getNamespace和CustomProperties重命名为bar和getBar。< / p>

请注意，您应该将@EnableConfigurationProperties应用于您的配置，以启用对@ConfigurationProperties的支持。然后，您可以使用该批注引用要处理的任何bean，而不是为它们提供@Bean方法，或使用@Component通过组件扫描发现它们：

@SpringBootApplication
@EnableConfigurationProperties(CustomProperties.class)
public class YourApplication {
    // …
}

Answer 2

我自己写了一个MapFilter类来有效地处理这个问题。实质上，您创建一个Map，然后通过指定密钥的前缀来过滤它。为方便起见，还有一个构造函数需要Properties。

请注意，这只会过滤主地图。应用于过滤后的地图的任何更改也会应用于基本地图，包括删除等，但显然主要地图的更改将不会反映在已过滤的地图中，直到某些内容导致重建。

过滤已过滤的地图也非常容易（也很有效）。

public class MapFilter<T> implements Map<String, T> {

    // The enclosed map -- could also be a MapFilter.
    final private Map<String, T> map;
    // Use a TreeMap for predictable iteration order.
    // Store Map.Entry to reflect changes down into the underlying map.
    // The Key is the shortened string. The entry.key is the full string.
    final private Map<String, Map.Entry<String, T>> entries = new TreeMap<>();
    // The prefix they are looking for in this map.
    final private String prefix;

    public MapFilter(Map<String, T> map, String prefix) {
        // Store my backing map.
        this.map = map;
        // Record my prefix.
        this.prefix = prefix;
        // Build my entries.
        rebuildEntries();
    }

    public MapFilter(Map<String, T> map) {
        this(map, "");
    }

    private synchronized void rebuildEntries() {
        // Start empty.
        entries.clear();
        // Build my entry set.
        for (Map.Entry<String, T> e : map.entrySet()) {
            String key = e.getKey();
            // Retain each one that starts with the specified prefix.
            if (key.startsWith(prefix)) {
                // Key it on the remainder.
                String k = key.substring(prefix.length());
                // Entries k always contains the LAST occurrence if there are multiples.
                entries.put(k, e);
            }
        }

    }

    @Override
    public String toString() {
        return "MapFilter (" + prefix + ") of " + map + " containing " + entrySet();
    }

    // Constructor from a properties file.
    public MapFilter(Properties p, String prefix) {
        // Properties extends HashTable<Object,Object> so it implements Map.
        // I need Map<String,T> so I wrap it in a HashMap for simplicity.
        // Java-8 breaks if we use diamond inference.
        this(new HashMap<String, T>((Map) p), prefix);
    }

    // Helper to fast filter the map.
    public MapFilter<T> filter(String prefix) {
        // Wrap me in a new filter.
        return new MapFilter<>(this, prefix);
    }

    // Count my entries.
    @Override
    public int size() {
        return entries.size();
    }

    // Are we empty.
    @Override
    public boolean isEmpty() {
        return entries.isEmpty();
    }

    // Is this key in me?
    @Override
    public boolean containsKey(Object key) {
        return entries.containsKey(key);
    }

    // Is this value in me.
    @Override
    public boolean containsValue(Object value) {
        // Walk the values.
        for (Map.Entry<String, T> e : entries.values()) {
            if (value.equals(e.getValue())) {
                // Its there!
                return true;
            }
        }
        return false;
    }

    // Get the referenced value - if present.
    @Override
    public T get(Object key) {
        return get(key, null);
    }

    // Get the referenced value - if present.
    public T get(Object key, T dflt) {
        Map.Entry<String, T> e = entries.get((String) key);
        return e != null ? e.getValue() : dflt;
    }

    // Add to the underlying map.
    @Override
    public T put(String key, T value) {
        T old = null;
        // Do I have an entry for it already?
        Map.Entry<String, T> entry = entries.get(key);
        // Was it already there?
        if (entry != null) {
            // Yes. Just update it.
            old = entry.setValue(value);
        } else {
            // Add it to the map.
            map.put(prefix + key, value);
            // Rebuild.
            rebuildEntries();
        }
        return old;
    }

    // Get rid of that one.
    @Override
    public T remove(Object key) {
        // Do I have an entry for it?
        Map.Entry<String, T> entry = entries.get((String) key);
        if (entry != null) {
            entries.remove(key);
            // Change the underlying map.
            return map.remove(prefix + key);
        }
        return null;
    }

    // Add all of them.
    @Override
    public void putAll(Map<? extends String, ? extends T> m) {
        for (Map.Entry<? extends String, ? extends T> e : m.entrySet()) {
            put(e.getKey(), e.getValue());
        }
    }

    // Clear everything out.
    @Override
    public void clear() {
        // Just remove mine.
        // This does not clear the underlying map - perhaps it should remove the filtered entries.
        for (String key : entries.keySet()) {
            map.remove(prefix + key);
        }
        entries.clear();
    }

    @Override
    public Set<String> keySet() {
        return entries.keySet();
    }

    @Override
    public Collection<T> values() {
        // Roll them all out into a new ArrayList.
        List<T> values = new ArrayList<>();
        for (Map.Entry<String, T> v : entries.values()) {
            values.add(v.getValue());
        }
        return values;
    }

    @Override
    public Set<Map.Entry<String, T>> entrySet() {
        // Roll them all out into a new TreeSet.
        Set<Map.Entry<String, T>> entrySet = new TreeSet<>();
        for (Map.Entry<String, Map.Entry<String, T>> v : entries.entrySet()) {
            entrySet.add(new Entry<>(v));
        }
        return entrySet;
    }

    /**
     * An entry.
     *
     * @param <T>
     *
     * The type of the value.
     */
    private static class Entry<T> implements Map.Entry<String, T>, Comparable<Entry<T>> {

        // Note that entry in the entry is an entry in the underlying map.
        private final Map.Entry<String, Map.Entry<String, T>> entry;

        Entry(Map.Entry<String, Map.Entry<String, T>> entry) {
            this.entry = entry;
        }

        @Override
        public String getKey() {
            return entry.getKey();
        }

        @Override
        public T getValue() {
            // Remember that the value is the entry in the underlying map.
            return entry.getValue().getValue();
        }

        @Override
        public T setValue(T newValue) {
            // Remember that the value is the entry in the underlying map.
            return entry.getValue().setValue(newValue);
        }

        @Override
        public boolean equals(Object o) {
            if (!(o instanceof Entry)) {
                return false;
            }
            Entry e = (Entry) o;
            return getKey().equals(e.getKey()) && getValue().equals(e.getValue());
        }

        @Override
        public int hashCode() {
            return getKey().hashCode() ^ getValue().hashCode();
        }

        @Override
        public String toString() {
            return getKey() + "=" + getValue();
        }

        @Override
        public int compareTo(Entry<T> o) {
            return getKey().compareTo(o.getKey());
        }
    }

    // Simple tests.
    public static void main(String[] args) {
        String[] samples = {
            "Some.For.Me",
            "Some.For.You",
            "Some.More",
            "Yet.More"};
        Map map = new HashMap();
        for (String s : samples) {
            map.put(s, s);
        }
        Map all = new MapFilter(map);
        Map some = new MapFilter(map, "Some.");
        Map someFor = new MapFilter(some, "For.");
        System.out.println("All: " + all);
        System.out.println("Some: " + some);
        System.out.println("Some.For: " + someFor);
    }
}

Answer 3

除此之外，我的问题是我没有多个简单的键/值属性，而是整个对象：

zuul:
  routes:
    query1:
      path: /api/apps/test1/query/**
      stripPrefix: false
      url: "https://test.url.com/query1"
    query2:
       path: /api/apps/test2/query/**
       stripPrefix: false
       url: "https://test.url.com/query2"
    index1:
       path: /api/apps/*/index/**
       stripPrefix: false
       url: "https://test.url.com/index"

按照杰克的建议，我试图将地图与Pojo一起使用，如下所示：

@ConfigurationProperties("zuul")
public class RouteConfig {
    private Map<String, Route> routes = new HashMap<>();

    public Map<String, Route> getRoutes() {
        return routes;
    }

    public static class Route {
        private String path;
        private boolean stripPrefix;
        String url;

        // [getters + setters]
    }
}

像魅力一样运作，谢谢！

Answer 4

我发疯了，试图理解为什么@Andy的answer对我不起作用（例如Map仍然是空的）只是为了意识到我有Lombok的@Builder注释方式，它添加了一个非空的构造函数。我要添加此答案，以强调为了使@ConfigurationProperties在Map上运行，值类型必须具有No-Arguments构造函数。在Spring的documentation中也提到了这一点：

这种安排依赖于默认的空构造函数，而getter和setter通常是强制性的...

我希望这可以节省其他人的时间。

使用ConfigurationProperties以通用方式填充Map

4 个答案: