4

我需要初始化需要包含的缓存

String in key
List<Object> in value

所以我有 CacheHelper 类

public class CacheHelper {

    private CacheManager cacheManager;

    private Cache<String,List<Person>> cacheDataList;

    private static final String CACHE_PERSON="cache_key_person";


    public CacheHelper() {


    }

    public void putInCacheFromDb(){
        System.getProperties().setProperty("java -Dnet.sf.ehcache.use.classic.lru", "true");
        cacheManager= CacheManagerBuilder
                .newCacheManagerBuilder().build();
        cacheManager.init();


        cacheDataList = cacheManager
                .createCache("cacheOfPersonList", CacheConfigurationBuilder
                        .newCacheConfigurationBuilder(
                                String.class,Person.class,
                                ResourcePoolsBuilder.heap(10)).withExpiry(Expirations.timeToLiveExpiration(Duration.of(60,
                                TimeUnit.SECONDS))));


    }


    public void putInList(List<Person> personList){
        System.out.println("putting list in cache");
        cacheDataList.put(CACHE_PERSON,personList);
    }


}

但是在这行代码中，我无法将对象转换为列表 String.class,Person.class，它需要是 String.class,List：

 cacheDataList = cacheManager
                    .createCache("cacheOfPersonList", CacheConfigurationBuilder
                            .newCacheConfigurationBuilder(
                                    String.class,Person.class,
                                    ResourcePoolsBuilder.heap(10)).withExpiry(Expirations.timeToLiveExpiration(Duration.of(60,
                                    TimeUnit.SECONDS))));

但我收到错误：

Incompatible types. Required Cache<String, List<Person>> but 'createCache' was inferred to Cache<K, V>: Incompatible equality constraint: List<Person> and Person

我需要将 List 存储在一个键中。如何初始化它？

4

1 回答 1

3

您将无法使用的内容，因为您将配置构建器定义为具有字符串键和人员值，而不是人员列表。泛型不允许您获取 List 类，因此您需要实现一个包装器：

import org.ehcache.Cache;
import org.ehcache.CacheManager;
import org.ehcache.config.builders.CacheConfigurationBuilder;
import org.ehcache.config.builders.CacheManagerBuilder;
import org.ehcache.config.builders.ResourcePoolsBuilder;
import org.ehcache.expiry.Expirations;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.TimeUnit;

public class CacheHelper {


    private CacheManager cacheManager;

    private Cache<String, PersonList> cacheDataList;

    private static final String CACHE_PERSON = "cache_key_person";

    private static class Person {
        final String name;

        public Person(final String name) {
            this.name = name;
        }
    }

    private class PersonList extends ArrayList<Person> {
        public PersonList(final Collection<? extends Person> c) {
            super(c);
        }
    }

    public static void main(String[] args) {


        List<Person> persons = new ArrayList<>();
        persons.add(new Person("Bob"));
        persons.add(new Person("Sally"));

        CacheHelper helper = new CacheHelper();
        helper.putInList(persons);
        PersonList personList = helper.cacheDataList.get(CACHE_PERSON);
        for (Person p : personList) {
            System.out.println("Found " + p.name);
        }

    }

    public CacheHelper() {
        System.getProperties().setProperty("java -Dnet.sf.ehcache.use.classic.lru", "true");
        cacheManager = CacheManagerBuilder
                .newCacheManagerBuilder().build();
        cacheManager.init();
        cacheDataList = cacheManager
                .createCache("cacheOfPersonList", CacheConfigurationBuilder
                        .newCacheConfigurationBuilder(String.class, PersonList.class, ResourcePoolsBuilder.heap(10))
                        .withExpiry(Expirations.timeToLiveExpiration(org.ehcache.expiry.Duration.of(20, TimeUnit.SECONDS))));
    }


    public void putInList(List<Person> personList) {
        System.out.println("putting list in cache");
        cacheDataList.put(CACHE_PERSON, new PersonList(personList));
    }


}
于 2019-09-05T04:04:50.733 回答