ehcache实例

代码结构

ColorDatabase.java

/*
 * All content copyright (c) Terracotta, Inc., except as may otherwise be noted in a separate copyright notice. All
 * rights reserved.
 */
package org.terracotta;

import java.awt.Color;
import java.util.Map;
import java.util.HashMap;

/**
 * This class simulates an external color database that is used to populate the
 * ColorCache. The primary, named AWT colors are stored in a map. Anytime a
 * color is requested and found, the calling thread is put to sleep for 3 seconds
 * to simulate a slow or overloaded database.
 */

public class ColorDatabase {
  private static final Map<String, Color> colorMap = new HashMap<String, Color>();

  static {
    colorMap.put("red", Color.red);
    colorMap.put("blue", Color.blue);
    colorMap.put("green", Color.green);
    colorMap.put("white", Color.white);
    colorMap.put("black", Color.black);
    colorMap.put("lightGray", Color.lightGray);
    colorMap.put("gray", Color.gray);
    colorMap.put("darkGray", Color.darkGray);
    colorMap.put("pink", Color.pink);
    colorMap.put("orange", Color.orange);
    colorMap.put("yellow", Color.yellow);
    colorMap.put("magenta", Color.magenta);
    colorMap.put("cyan", Color.cyan);
  }

  public ColorDatabase() {
    
  }

  /**
   * Simulates retrieving expensive object from SOR.
   */
  public Color getColor(String name) {
    Color color = colorMap.get(name);
    if(color == null) {
      return null;
    }
    try {
      Thread.sleep(3000);
    } catch(Exception e) {}
    return color;
  }
}

ColorCache.java

/*
 * All content copyright (c) Terracotta, Inc., except as may otherwise be noted in a separate copyright notice. All
 * rights reserved.
 */
package org.terracotta;

import net.sf.ehcache.*;

import java.awt.Color;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class ColorCache {
  private static final CacheManager  cacheManager  = new CacheManager();
  private static final ColorDatabase colorDatabase = new ColorDatabase();

  public ColorCache() {
    /**/
  }

  public Color getColor(String name) {
    Element elem = getCache().get(name);
    if (elem == null) {
      Color color = colorDatabase.getColor(name);
      if (color == null) { return null; }
      getCache().put(elem = new Element(name, color));
    }
    return (Color) elem.getValue();
  }

  private Color getCachedColor(String name) {
    Element elem = getCache().get(name);
    return elem != null ? (Color) elem.getValue() : null;
  }

  public String[] getColorNames() {
    @SuppressWarnings("unchecked")
    Iterator<String> keys = ((List<String>) getCache().getKeys()).iterator();
    List<String> list = new ArrayList<String>();
    while (keys.hasNext()) {
      String name = keys.next();
      if (getCachedColor(name) != null) {
        list.add(name);
      }
    }
    return list.toArray(new String[list.size()]);
  }

  public long getTTL() {
    return getCache().getCacheConfiguration().getTimeToLiveSeconds();
  }

  public long getTTI() {
    return getCache().getCacheConfiguration().getTimeToIdleSeconds();
  }

  public int getSize() {
    return getCache().getSize();
  }

  private Ehcache getCache() {
    return cacheManager.getEhcache("colors");
  }
}

ehcache.xml 放在类加载路径上：

<?xml version="1.0" encoding="UTF-8"?>


<ehcache>

    <diskStore path="java.io.tmpdir"/>
    <defaultCache
        maxElementsInMemory="10000"
        eternal="false"
        timeToIdleSeconds="120"
        timeToLiveSeconds="120"
        overflowToDisk="true"
        />
    <cache name="colors"
         maxElementsInMemory="100"
         maxElementsOnDisk="0"
         eternal="false"
         timeToIdleSeconds="120"
         timeToLiveSeconds="0">
    </cache>
    
    <cache name="sampleCache1"
        maxElementsInMemory="10000"
        eternal="false"
        timeToIdleSeconds="300"
        timeToLiveSeconds="600"
        overflowToDisk="true"
        />
    <cache name="sampleCache2"
        maxElementsInMemory="1000"
        eternal="true"
        timeToIdleSeconds="0"
        timeToLiveSeconds="0"
        overflowToDisk="false"
        /> 
</ehcache>

Test.java

package org.terracotta;

import java.awt.Color;

public class Test {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		ColorCache cache = new ColorCache();
		
		 long now = System.currentTimeMillis();
		 Color red=cache.getColor("red");
		 long elapsed = System.currentTimeMillis() - now;
		 //第一次获取数据时间为：
		 System.out.println("第一次获取数据时间为："+elapsed+"---"+red);
		 
		 long now2 = System.currentTimeMillis();
		 Color red2=cache.getColor("red");
		 long elapsed2 = System.currentTimeMillis() - now2;
		 //第2次获取数据时间为：
		 System.out.println("第2次获取数据时间为："+elapsed2+"---"+red2);
		 
	}

}

测试结果：

第一次获取数据时间为：3003---java.awt.Color[r=255,g=0,b=0]
第2次获取数据时间为：0---java.awt.Color[r=255,g=0,b=0]