jface databinding:List,Set,Map对象的Observable代理封装

需求描述

对于一个已经存在的集合/映射对象(普通的List,Set,Map,非observable),我们希望把将它转换成一个observable对象，这个observable对象就像是原对象的代理一样，当对observable对象操作(增加删除元素)时，实际是对原对象的操作。
jface为List,Set,Map三种类型提供了对应的三种可写对象WritableList,WritableSet,WritableMap，研究了这三个类的代码，发现它们99%是满足这个需求，然并卵，因为构造函数上设计区别，造成这三个类的构造函数生成的observable对象与原对象是隔离的。
以WritableSet的构造函数为例,WritableSet的构造函数重新用外部传入的Collection的内容构造了一个新的HashSet对象，所以WritableSet中的Set对象与传入的原对象(Collection)没有半毛钱关系：

    public WritableSet(Realm realm, Collection c, Object elementType) {
        // 创建了一个新的Set对象传给父类的构造函数
        super(realm, new HashSet(c), elementType);
        this.elementType = elementType;
    }

只有WritableList类可以实现的上述的需求,而且貌似还是为了兼容之前版本的设计失误，而留的。
参见下面WritableList的构造函数的说明org.eclipse.core.databinding.observable.list.WritableList.WritableList(Realm realm, List toWrap, Object elementType)

    /** * Creates a writable list containing elements of the given type, wrapping * an existing client-supplied list. Note that for backwards compatibility * reasons, the contents of the created WritableList will change with the * contents of the given list. If this is not desired, * {@link #WritableList(Realm, Collection, Object)} should be used by * casting the second argument to {@link Collection}. * * @param realm * the observable's realm * @param toWrap * The java.util.List to wrap * @param elementType * can be null */
    public WritableList(Realm realm, List toWrap, Object elementType) {
        // 没有对toWrap做任何处理就传给了父类的构造函数，这才是我想要的
        super(realm, toWrap, elementType);
    }

所以这虽然是一个很普遍的需求，但jface并没有提供完整的支持，需要自己写代码支持。好在jface的基础框架比较扎实，所以如果搞清楚jface的类继承结构，自己写代码也不复杂，所以我为List,Set,Map三种类型的分别写了三个类用于实现Observable封装(WrappedObservableList,WrappedObservableSet,WrappedObservableMap),这三个类的代码都参考自对应的WritableList,WritableSet,WritableMap三个类，大部分代码都是直接抄来的。以下是三个类对应的实现代码

WrappedObservableList

WrappedObservableList类实现最简单，因为WritableList本身就因为历史原因支持这种代理封装，所以WrappedObservableList类只是在构造函数中加了参数检查
WrappedObservableList.java

package net.gdface.ui.binding;

import java.util.List;
import java.util.Objects;

import org.eclipse.core.databinding.observable.Realm;
import org.eclipse.core.databinding.observable.list.WritableList;

/** * 将指定的{@link List}对象(wrappedList)封装为 {@link ObservableList},
 * 对observable对象的操作同步到原对象
 * @author guyadong * * @param  */
public class WrappedObservableList<E> extends WritableList<E> {

    public WrappedObservableList(List wrappedList, Object elementType) {
        this(Realm.getDefault(),wrappedList, elementType);
    }

    public WrappedObservableList(Realm realm, List wrappedList, Object elementType) {
        super(realm, Objects.requireNonNull(wrappedList,"the argument wrappedList must not be null"), elementType);
    }   
}

WrappedObservableSet

WrappedObservableSet类的大部分代码都抄自WritableSet
WrappedObservableSet.java

package net.gdface.ui.binding;

import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Objects;
import java.util.Set;

import org.eclipse.core.databinding.observable.Diffs;
import org.eclipse.core.databinding.observable.Realm;
import org.eclipse.core.databinding.observable.set.ObservableSet;

/** * 将指定的{@link Set}对象(wrappedSet)封装为 {@link ObservableSet},
 * 对observable对象的操作同步到原对象
 * override方法实现代码抄自{@link org.eclipse.core.databinding.observable.set.WritableSet} * @author guyadong * * @param  */
public class WrappedObservableSet<E> extends ObservableSet<E>{

    /** * @param realm * @param wrappedSet 为null抛出异常 * @param elementType */
    protected WrappedObservableSet(Realm realm, Set wrappedSet, Object elementType) {
        super(realm, Objects.requireNonNull(wrappedSet,"the argument wrappedSet must not be null"), elementType);       
    }

    public WrappedObservableSet(Set wrappedSet, Object elementType) {
        this(Realm.getDefault(),wrappedSet, elementType);
    }
    public WrappedObservableSet(Set wrappedSet) {
        this(Realm.getDefault(),wrappedSet, null);
    }
    @Override
    public boolean add(E o) {
        getterCalled();
        boolean added = wrappedSet.add(o);
        if (added) {
            Set removals = Collections.emptySet();
            fireSetChange(Diffs.createSetDiff(Collections.singleton(o), removals));
        }
        return added;
    }

    @Override
    public boolean addAll(Collection c) {
        getterCalled();
        Set additions = new HashSet();
        Iterator it = c.iterator();
        while (it.hasNext()) {
            E element = it.next();
            if (wrappedSet.add(element)) {
                additions.add(element);
            }
        }
        if (additions.size() > 0) {
            Set removals = Collections.emptySet();
            fireSetChange(Diffs.createSetDiff(additions, removals));
            return true;
        }
        return false;
    }

    @SuppressWarnings("unchecked")
    @Override
    public boolean remove(Object o) {
        getterCalled();
        boolean removed = wrappedSet.remove(o);
        if (removed) {
            Set additions = Collections.emptySet();
            fireSetChange(Diffs.createSetDiff(additions,
                    Collections.singleton((E) o)));
        }
        return removed;
    }

    @SuppressWarnings("unchecked")
    @Override
    public boolean removeAll(Collection c) {
        getterCalled();
        Set removes = new HashSet();
        Iterator it = c.iterator();
        while (it.hasNext()) {
            Object element = it.next();
            if (wrappedSet.remove(element)) {
                removes.add((E) element);
            }
        }
        if (removes.size() > 0) {
            Set additions = Collections.emptySet();
            fireSetChange(Diffs.createSetDiff(additions, removes));
            return true;
        }
        return false;
    }

    @Override
    public boolean retainAll(Collection c) {
        getterCalled();
        Set removes = new HashSet();
        Iterator it = wrappedSet.iterator();
        while (it.hasNext()) {
            E element = it.next();
            if (!c.contains(element)) {
                it.remove();
                removes.add(element);
            }
        }
        if (removes.size() > 0) {
            Set additions = Collections.emptySet();
            fireSetChange(Diffs.createSetDiff(additions, removes));
            return true;
        }
        return false;
    }

    @Override
    public void clear() {
        getterCalled();
        Set removes = new HashSet(wrappedSet);
        Set additions = Collections.emptySet();
        wrappedSet.clear();
        fireSetChange(Diffs.createSetDiff(additions, removes));
    }
}

WrappedObservableMap

WrappedObservableMap的大部分代码也都是抄自WritableMap
WrappedObservableMap.java

package net.gdface.ui.binding;

import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Objects;
import java.util.Set;

import org.eclipse.core.databinding.observable.Diffs;
import org.eclipse.core.databinding.observable.Realm;
import org.eclipse.core.databinding.observable.map.MapDiff;
import org.eclipse.core.databinding.observable.map.ObservableMap;
import org.eclipse.core.internal.databinding.observable.Util;

/** * 将指定的{@link Map}对象(wrappedMap)封装为 {@link ObservableMap},
 * 对observable对象的操作同步到原对象
 * override方法实现代码抄自 {@link org.eclipse.core.databinding.observable.map.WritableMap} * @author guyadong * * @param  * @param  */
public class WrappedObservableMap<K, V> extends ObservableMap<K, V> {

    private final Object keyType;
    private final Object valueType;

    public WrappedObservableMap(Map wrappedMap) {
        this(Realm.getDefault(),wrappedMap, null, null);
    }

    public WrappedObservableMap(Map wrappedMap, Object keyType, Object valueType) {
        this(Realm.getDefault(),wrappedMap, keyType, valueType);
    }
    /** * @param realm * @param wrappedMap 为null抛出异常 * @param keyType * @param valueType */
    public WrappedObservableMap(Realm realm, Map wrappedMap, Object keyType, Object valueType) {
        super(realm, Objects.requireNonNull(wrappedMap,"the argument wrappedMap must not be null"));
        this.keyType=keyType;
        this.valueType=valueType;
    }

    @Override
    public Object getKeyType() {
        return keyType;
    }

    @Override
    public Object getValueType() {
        return valueType;
    }
    @Override
    public V put(K key, V value) {
        checkRealm();

        boolean containedKeyBefore = wrappedMap.containsKey(key);
        V result = wrappedMap.put(key, value);
        boolean containedKeyAfter = wrappedMap.containsKey(key);

        if (containedKeyBefore != containedKeyAfter
                || !Util.equals(result, value)) {
            MapDiff diff;
            if (containedKeyBefore) {
                if (containedKeyAfter) {
                    diff = Diffs.createMapDiffSingleChange(key, result, value);
                } else {
                    diff = Diffs.createMapDiffSingleRemove(key, result);
                }
            } else {
                diff = Diffs.createMapDiffSingleAdd(key, value);
            }
            fireMapChange(diff);
        }
        return result;
    }

    @SuppressWarnings("unchecked")
    @Override
    public V remove(Object key) {
        checkRealm();
        if (wrappedMap.containsKey(key)) {
            V result = wrappedMap.remove(key);
            fireMapChange(Diffs.createMapDiffSingleRemove((K) key, result));
            return result;
        }
        return null;
    }

    @Override
    public void clear() {
        checkRealm();
        if (!isEmpty()) {
            Map copy = new HashMap<>(wrappedMap);
            wrappedMap.clear();
            fireMapChange(Diffs.createMapDiffRemoveAll(copy));
        }
    }

    @Override
    public void putAll(Map map) {
        checkRealm();
        Set addedKeys = new HashSet<>(map.size());
        Map changes = new HashMap<>(map.size());
        for (Map.Entry entry : map.entrySet()) {
            boolean add = !wrappedMap.containsKey(entry.getKey());
            V previousValue = wrappedMap.put(entry.getKey(), entry.getValue());
            if (add) {
                addedKeys.add(entry.getKey());
            } else {
                changes.put(entry.getKey(), previousValue);
            }
        }
        if (!addedKeys.isEmpty() || !changes.isEmpty()) {
            Set removedKeys = Collections.emptySet();
            fireMapChange(Diffs.createMapDiff(addedKeys, removedKeys,
                    changes.keySet(), changes, wrappedMap));
        }
    }

}

注意

上面代码中使用了java8才有方法，所以要在java8下编译