为了提升项目的并发性能,考虑引入本地内存Cache,对:外部数据源访问、Restful API调用、可重用的复杂计算 等3种类型的函数处理结果进行缓存。目前采用的是Spring Cache的@Cacheable注解方式,缓存具体实现选取的是Guava Cache。
具体缓存的配置此处不再介绍,重点对于key的配置进行说明:
1、基本形式
-
@Cacheable(value=
"cacheName", key
"#id")
-
public ResultDTO method(int id);
2、组合形式
-
@Cacheable(value=
"cacheName", key
"T(String).valueOf(#name).concat('-').concat(#password))
-
public ResultDTO method(int name, String password);
-
3、对象形式
-
@Cacheable(value=
"cacheName", key
"#user.id)
-
public ResultDTO method(User user);
-
4、自定义Key生成器
-
@Cacheable(value=
"gomeo2oCache", keyGenerator =
"keyGenerator")
-
public ResultDTO method(User user);
有一个尤其需要注意的坑:Spring默认的SimpleKeyGenerator是不会将函数名组合进key中的
举个栗子:
-
@Component
-
public
class CacheTestImpl implements CacheTest {
-
@Cacheable(
"databaseCache")
-
public Long test1()
-
{
return
1L; }
-
-
@Cacheable(
"databaseCache")
-
public Long test2()
-
{
return
2L; }
-
-
@Cacheable(
"databaseCache")
-
public Long test3()
-
{
return
3L; }
-
-
@Cacheable(
"databaseCache")
-
public String test4()
-
{
return
"4"; }
-
-
}
我们期望的输出是:
而实际上的输出是:
1 2 3 4
1 1 1 ClassCastException: java.lang.Long cannot be cast to java.lang.String
为了解决上述2个问题,自定义了一个KeyGenerator如下:
-
class CacheKeyGenerator implements KeyGenerator {
-
-
// custom cache key
-
public
static
final
int NO_PARAM_KEY =
0;
-
public
static
final
int NULL_PARAM_KEY =
53;
-
-
@Override
-
public Object generate(Object target, Method method, Object... params) {
-
-
StringBuilder key =
new StringBuilder();
-
key.append(target.getClass().getSimpleName()).append(
".").append(method.getName()).append(
":");
-
if (params.length ==
0) {
-
return key.append(NO_PARAM_KEY).toString();
-
}
-
for (Object param : params) {
-
if (param ==
null) {
-
log.warn(
"input null param for Spring cache, use default key={}", NULL_PARAM_KEY);
-
key.append(NULL_PARAM_KEY);
-
}
else
if (ClassUtils.isPrimitiveArray(param.getClass())) {
-
int length = Array.getLength(param);
-
for (
int i =
0; i < length; i++) {
-
key.append(Array.get(param, i));
-
key.append(
',');
-
}
-
}
else
if (ClassUtils.isPrimitiveOrWrapper(param.getClass()) || param
instanceof String) {
-
key.append(param);
-
}
else {
-
log.warn(
"Using an object as a cache key may lead to unexpected results. " +
-
"Either use @Cacheable(key=..) or implement CacheKey. Method is " + target.getClass() +
"#" + method.getName());
-
key.append(param.hashCode());
-
}
-
key.append(
'-');
-
}
-
-
String finalKey = key.toString();
-
long cacheKeyHash = Hashing.murmur3_128().hashString(finalKey, Charset.defaultCharset()).asLong();
-
log.debug(
"using cache key={} hashCode={}", finalKey, cacheKeyHash);
-
return key.toString();
-
}
-
}
采用此方式后可以解决:多参数、原子类型数组、方法名识别 等问题