设计模式课程 设计模式精讲 14-3 组合模式源码解析

1　　　　源码解析

1.1　　jdk源码解析之Container

1.2　　jdk源码解析之HashMap

1.3　　jdk源码解析之ArrayList

1.4　　mybaties源码解析之SqlNode

1　　　　源码解析

1.1　　jdk源码解析之Container

//实现窗口菜单，属于编写cs软件结构时所使用的
//该方法将相同类型的接口类型或者抽象类类型转化为树状结构
public class Container extends Component { 
/**
     * Appends the specified component to the end of this container.
     * This is a convenience method for {@link #addImpl}.
     * <p>
     * This method changes layout-related information, and therefore,
     * invalidates the component hierarchy. If the container has already been
     * displayed, the hierarchy must be validated thereafter in order to
     * display the added component.
     *
     * @param     comp   the component to be added
     * @exception NullPointerException if {@code comp} is {@code null}
     * @see #addImpl
     * @see #invalidate
     * @see #validate
     * @see javax.swing.JComponent#revalidate()
     * @return    the component argument
     */
    public Component add(Component comp) {
        addImpl(comp, null, -1);
        return comp;
    }
}

1.2　　jdk源码解析之HashMap

 
public class HashMap<K,V>
    extends AbstractMap<K,V>
    implements Map<K,V>, Cloneable, Serializable
{

 /**
     * Copies all of the mappings from the specified map to this map.
     * These mappings will replace any mappings that this map had for
     * any of the keys currently in the specified map.
     *
     * @param m mappings to be stored in this map
     * @throws NullPointerException if the specified map is null
     */
    public void putAll(Map<? extends K, ? extends V> m) {
        int numKeysToBeAdded = m.size();
        if (numKeysToBeAdded == 0)
            return;

        if (table == EMPTY_TABLE) {
            inflateTable((int) Math.max(numKeysToBeAdded * loadFactor, threshold));
        }

        /*
         * Expand the map if the map if the number of mappings to be added
         * is greater than or equal to threshold.  This is conservative; the
         * obvious condition is (m.size() + size) >= threshold, but this
         * condition could result in a map with twice the appropriate capacity,
         * if the keys to be added overlap with the keys already in this map.
         * By using the conservative calculation, we subject ourself
         * to at most one extra resize.
         */
        if (numKeysToBeAdded > threshold) {
            int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1);
            if (targetCapacity > MAXIMUM_CAPACITY)
                targetCapacity = MAXIMUM_CAPACITY;
            int newCapacity = table.length;
            while (newCapacity < targetCapacity)
                newCapacity <<= 1;
            if (newCapacity > table.length)
                resize(newCapacity);
        }

        for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
            put(e.getKey(), e.getValue());
    }
}

1.3　　jdk源码解析之ArrayList

ArrayList实现了List，List继承了Conllection，所以ArrayList的addAll方法可以看作组合方式的应用

ArrayList

public class ArrayList<E> extends AbstractList<E>
        implements List<E>, RandomAccess, Cloneable, java.io.Serializable
{
 public boolean addAll(Collection<? extends E> c) {
        Object[] a = c.toArray();
        int numNew = a.length;
        ensureCapacityInternal(size + numNew);  // Increments modCount
        System.arraycopy(a, 0, elementData, size, numNew);
        size += numNew;
        return numNew != 0;
    }

}

List

public interface List<E> extends Collection<E> {

}

1.4　　mybaties源码解析之SqlNode

 对比14-2去看

SqlNode接口：

package org.apache.ibatis.scripting.xmltags;

public interface SqlNode {
    boolean apply(DynamicContext var1);
}

MixedSqlNode实现类：

/**
 *    Copyright 2009-2015 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package org.apache.ibatis.scripting.xmltags;

import java.util.List;

/**
 * @author Clinton Begin
 */
public class MixedSqlNode implements SqlNode {
  private List<SqlNode> contents;

  public MixedSqlNode(List<SqlNode> contents) {
    this.contents = contents;
  }

  @Override
  public boolean apply(DynamicContext context) {
    for (SqlNode sqlNode : contents) {
      sqlNode.apply(context);//此处和14-2的print是异曲同工的
    }
    return true;
  }
}

WhereSqlNode实现类（引入apply方法）：

/**
 *    Copyright 2009-2015 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package org.apache.ibatis.scripting.xmltags;

import java.util.Arrays;
import java.util.List;

import org.apache.ibatis.session.Configuration;

/**
 * @author Clinton Begin
 */
public class WhereSqlNode extends TrimSqlNode {

  private static List<String> prefixList = Arrays.asList("AND ","OR ","AND
", "OR
", "AND
", "OR
", "AND	", "OR	");

  public WhereSqlNode(Configuration configuration, SqlNode contents) {
    super(configuration, contents, "WHERE", prefixList, null, null);
  }

}

TrimSqlNode（调到apply方法）

public class TrimSqlNode implements SqlNode {

public TrimSqlNode(Configuration configuration, SqlNode contents, String prefix, String prefixesToOverride, String suffix, String suffixesToOverride) {
    this(configuration, contents, prefix, parseOverrides(prefixesToOverride), suffix, parseOverrides(suffixesToOverride));
  }

protected TrimSqlNode(Configuration configuration, SqlNode contents, String prefix, List<String> prefixesToOverride, String suffix, List<String> suffixesToOverride) {
    this.contents = contents;
    this.prefix = prefix;
    this.prefixesToOverride = prefixesToOverride;
    this.suffix = suffix;
    this.suffixesToOverride = suffixesToOverride;
    this.configuration = configuration;
  }

  @Override
  public boolean apply(DynamicContext context) {
    FilteredDynamicContext filteredDynamicContext = new FilteredDynamicContext(context);
    boolean result = contents.apply(filteredDynamicContext);
    filteredDynamicContext.applyAll();
    return result;
  }

public void applyAll() {
  sqlBuffer = new StringBuilder(sqlBuffer.toString().trim());
  String trimmedUppercaseSql = sqlBuffer.toString().toUpperCase(Locale.ENGLISH);
  if (trimmedUppercaseSql.length() > 0) {
    applyPrefix(sqlBuffer, trimmedUppercaseSql);
    applySuffix(sqlBuffer, trimmedUppercaseSql);
  }
  delegate.appendSql(sqlBuffer.toString());
}

}