增加LoadingCache示例

Author: chenhuawei

guava/pom.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>tutorial-java</artifactId>
+        <groupId>biz.chenxu</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>guava</artifactId>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>18.0</version>
+        </dependency>
+    </dependencies>
+
+</project>

guava/src/main/java/biz/chenxu/tutorial/LoadingCacheTutorial.java

@@ -0,0 +1,86 @@
+package biz.chenxu.tutorial;
+
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
+
+import java.util.Map;
+import java.util.concurrent.ExecutionException;
+
+public class LoadingCacheTutorial {
+
+    private LoadingCache<String, String> loadingCache;
+
+    private int counter;
+
+    private static LoadingCacheTutorial instance = new LoadingCacheTutorial();
+
+    public static LoadingCacheTutorial getInstance() {
+        return instance;
+    }
+
+    private LoadingCacheTutorial() {
+        loadingCache = CacheBuilder.newBuilder()
+                .maximumSize(3)
+                .build(new CacheLoader<String, String>() {
+
+                    @Override
+                    public String load(String key) throws Exception {
+                        System.out.println(String.format("loading not exist key [%s]", key));
+                        return String.format("cache value %d", counter++);
+                    }
+                });
+    }
+
+    public String getCacheValueIfExist(String key) {
+        return loadingCache.getIfPresent(key);
+    }
+
+    public String getCacheValue(String key) {
+        try {
+            return loadingCache.get(key);
+        } catch (ExecutionException e) {
+            e.printStackTrace();
+            return null;
+        }
+    }
+
+    public void dump() {
+        System.out.println("***begin dump cache content***");
+        for (Map.Entry<String, String> entry : loadingCache.asMap().entrySet()) {
+            System.out.println(String.format("%s = %s", entry.getKey(), entry.getValue()));
+        }
+        System.out.println("***end dump cache content***");
+    }
+
+    public static void main(String[] args) {
+
+        // load notExistKey1
+        String notExistKey1 = "notExistKey1";
+        String notExistValue1 = LoadingCacheTutorial.getInstance().getCacheValue(notExistKey1);
+        System.out.println(String.format("1.%s = %s", notExistKey1, notExistValue1));
+
+        // don't load notExistKey2
+        String notExistKey2 = "notExistKey2";
+        String notExistValue2 = LoadingCacheTutorial.getInstance().getCacheValueIfExist(notExistKey2);
+        System.out.println(String.format("2.%s = %s", notExistKey2, notExistValue2));
+
+        // LRU
+        // load notExistKey2
+        LoadingCacheTutorial.getInstance().getCacheValue(notExistKey2);
+        LoadingCacheTutorial.getInstance().dump();
+
+        System.err.println("[Warn] the key2 will be removed by LRU strategy ......");
+        // use key1
+        LoadingCacheTutorial.getInstance().getCacheValue(notExistKey1);
+        LoadingCacheTutorial.getInstance().getCacheValue(notExistKey1);
+
+        // load notExistKey3
+        LoadingCacheTutorial.getInstance().getCacheValue("notExistKey3");
+
+        // load notExistKey4
+        LoadingCacheTutorial.getInstance().getCacheValue("notExistKey4");
+
+        LoadingCacheTutorial.getInstance().dump();
+    }
+}

pom.xml

@@ -12,6 +12,7 @@
     <modules>
         <module>http-async-client</module>
         <module>fast-json</module>
+        <module>guava</module>
     </modules>
 
     <properties>