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我正在开发一个类似 Redis 的开源 Memcache API：http ://bit.ly/XVfpRX

谁能帮我分析一下为什么这段代码的String field andString value变量的值是错误的：

public Long hset(String key, String field, String value) {
    System.out.println("HSET key="+key+" field=" + field + " value="+value);
    try {
        boolean exist = exists(key);
        if(exist){
            Set<Tuple<String,String>> hash = (Set<Tuple<String,String>>) memget(key);
            Iterator<Tuple<String, String>> it = hash.iterator();
            while (it.hasNext()){
                Tuple<String, String> t = it.next();
                if (t.getFirst().equals(field)){
                    System.out.println("HSET Removing field=" + t.getFirst() + " value="+t.getSecond());
                    hash.remove(t);
                    hash.add(new Tuple<String, String>(field, value));
                }
            }
            memset(key, hash);
            return 0L;
        } else {
            Set<Tuple<String,String>> hash = new HashSet<Tuple<String,String>>();
            System.out.println("Adding new tuple key="+key+" field=" + field + " value="+value);
            hash.add(new Tuple<String, String>(field, value));
            memset(key, hash);  
            return 1L;
        }
    } catch(Exception e) { //  ClassCastException and NPE
        // What to do when CCE is encountered?
        Set<Tuple<String,String>> hash = new HashSet<Tuple<String,String>>();
        hash.add(new Tuple<String, String>(field, value));
        memset(key, hash);              
    } 
    return 1L;
}

以下是测试日志：

Start hset tests
HSET key=null field=null value=null
Adding new tuple key=null field=null value=null
MEMSET key=null value=[Tuple [first=null, second=null]]
HSET key=foo field=foo value=bar
Adding new tuple key=foo field=foo value=bar
MEMSET key=foo value=[Tuple [first=foo, second=bar]]
HSET key=foo field=bar value=foobar
MEMSET key=foo value=[Tuple [first=foo, second=bar]]
HSET key=user:1 field=uname value=foo
Adding new tuple key=user:1 field=uname value=foo
MEMSET key=user:1 value=[Tuple [first=uname, second=foo]]
HSET key=user:1 field=fname value=Bar
MEMSET key=user:1 value=[Tuple [first=uname, second=foo]]
HSET key=user:1 field=uname value=bar
HSET Removing field=uname value=foo
MEMSET key=user:1 value=[Tuple [first=uname, second=bar]]

还有实际的 JUnit 测试：

@Test
public void testHset() {
    System.out.println("Start hset tests");
    Long ret = lingo.hset(key, null, value);
    assertEquals(1L, ret.longValue());
    ret = lingo.hset("foo", "foo", "bar");
    assertEquals(1L, ret.longValue());
    ret = lingo.hset("foo", "bar", "foobar");
    assertEquals(0L, ret.longValue());

    ret = lingo.hset("user:1", "uname", "foo");
    assertEquals(1L, ret.longValue());
    ret = lingo.hset("user:1", "fname", "Bar");
    assertEquals(0L, ret.longValue());
    ret = lingo.hset("user:1", "uname", "bar");
    assertEquals(0L, ret.longValue());

    String username = lingo.hget("user:1", "uname");
    String firstname = lingo.hget("user:1", "fname");
    assertEquals("bar", username);
    assertEquals("Bar", firstname);
    System.out.println("End hset tests");
}

问题区域是这样的：

HSET key=foo field=bar value=foobar
MEMSET key=foo value=[Tuple [first=foo, second=bar]]

还有这个：

HSET key=user:1 field=fname value=Bar
MEMSET key=user:1 value=[Tuple [first=uname, second=foo]]

传播到 memset（这是 GAE memcache put 的键值对包装方法）的字段和值是错误的。

元组代码可以在这里找到。

更新（添加 hget 方法）：

public String hget(String key, String field) {
    try {
        boolean exist = exists(key);
        if(exist){
            Set<Tuple<String,String>> hash = (Set<Tuple<String,String>>) memget(key);
            Iterator<Tuple<String, String>> it = hash.iterator();
            while (it.hasNext()){
                Tuple<String, String> t = it.next();
                if (t.getFirst().equals(field)){
                    return t.getSecond();
                }
            }
        } 
    } catch(Exception e) { //  ClassCastException and NPE
        // What to do when CCE is encountered?
    } 
    return "nil";
}
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1 回答 1

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你写了那Tuple节课吗？

我的第一个想法是您没有正确equals覆盖hashCode。Joshua Bloch 的Effective Java告诉您如何操作。

于 2013-04-24T23:08:01.710 回答