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

た入场券 2022-07-13 10:21 64阅读 0赞

# 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<? extends E> 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<E>(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<E> 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 <code>null</code>
 */
 public WritableList(Realm realm, List<E> 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 <E>
 */
 public class WrappedObservableList<E> extends WritableList<E> {
 
 
 public WrappedObservableList(List<E> wrappedList, Object elementType) {
 this(Realm.getDefault(),wrappedList, elementType);
 }
 
 public WrappedObservableList(Realm realm, List<E> 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 <E>
 */
 public class WrappedObservableSet<E> extends ObservableSet<E>{
 
 
 /**
 * @param realm
 * @param wrappedSet 为null抛出异常
 * @param elementType
 */
 protected WrappedObservableSet(Realm realm, Set<E> wrappedSet, Object elementType) {
 super(realm, Objects.requireNonNull(wrappedSet,"the argument wrappedSet must not be null"), elementType); 
 }
 
 public WrappedObservableSet(Set<E> wrappedSet, Object elementType) {
 this(Realm.getDefault(),wrappedSet, elementType);
 }
 public WrappedObservableSet(Set<E> wrappedSet) {
 this(Realm.getDefault(),wrappedSet, null);
 }
 @Override
 public boolean add(E o) {
 getterCalled();
 boolean added = wrappedSet.add(o);
 if (added) {
 Set<E> removals = Collections.emptySet();
 fireSetChange(Diffs.createSetDiff(Collections.singleton(o), removals));
 }
 return added;
 }
 
 @Override
 public boolean addAll(Collection<? extends E> c) {
 getterCalled();
 Set<E> additions = new HashSet<E>();
 Iterator<? extends E> it = c.iterator();
 while (it.hasNext()) {
 E element = it.next();
 if (wrappedSet.add(element)) {
 additions.add(element);
 }
 }
 if (additions.size() > 0) {
 Set<E> 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<E> additions = Collections.emptySet();
 fireSetChange(Diffs.createSetDiff(additions,
 Collections.singleton((E) o)));
 }
 return removed;
 }
 
 @SuppressWarnings("unchecked")
 @Override
 public boolean removeAll(Collection<?> c) {
 getterCalled();
 Set<E> removes = new HashSet<E>();
 Iterator<?> it = c.iterator();
 while (it.hasNext()) {
 Object element = it.next();
 if (wrappedSet.remove(element)) {
 removes.add((E) element);
 }
 }
 if (removes.size() > 0) {
 Set<E> additions = Collections.emptySet();
 fireSetChange(Diffs.createSetDiff(additions, removes));
 return true;
 }
 return false;
 }
 
 @Override
 public boolean retainAll(Collection<?> c) {
 getterCalled();
 Set<E> removes = new HashSet<E>();
 Iterator<E> it = wrappedSet.iterator();
 while (it.hasNext()) {
 E element = it.next();
 if (!c.contains(element)) {
 it.remove();
 removes.add(element);
 }
 }
 if (removes.size() > 0) {
 Set<E> additions = Collections.emptySet();
 fireSetChange(Diffs.createSetDiff(additions, removes));
 return true;
 }
 return false;
 }
 
 @Override
 public void clear() {
 getterCalled();
 Set<E> removes = new HashSet<E>(wrappedSet);
 Set<E> 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 <K>
 * @param <V>
 */
 public class WrappedObservableMap<K, V> extends ObservableMap<K, V> {
 
 
 private final Object keyType;
 private final Object valueType;
 
 public WrappedObservableMap(Map<K, V> wrappedMap) {
 this(Realm.getDefault(),wrappedMap, null, null);
 }
 
 public WrappedObservableMap(Map<K, V> 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<K, V> 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<K, V> 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<K, V> copy = new HashMap<>(wrappedMap);
 wrappedMap.clear();
 fireMapChange(Diffs.createMapDiffRemoveAll(copy));
 }
 }
 
 @Override
 public void putAll(Map<? extends K, ? extends V> map) {
 checkRealm();
 Set<K> addedKeys = new HashSet<>(map.size());
 Map<K, V> changes = new HashMap<>(map.size());
 for (Map.Entry<? extends K, ? extends V> 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<K> 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