java 泛型List擦除问题（解决方案）

╰+哭是因爲堅強的太久メ 2022-07-15 07:30 200阅读 0赞

java和c\#比较，会有一个被C\#耻笑的问题，就是java的泛型传入List时会被擦除,书上是这样解释的：

![这里写图片描述][20161108123207619]

代码示例如下：

public abstract class AbstractOp implements Operation \{

@Override
    public T get(String customKey) {
        String vStr = CacheUtil.get(getKey(customKey));
        if (null == vStr) {
            T vObj = this.getBizValue(customKey);
            CacheUtil.put(getKey(customKey),    JSON.toJSONString(vObj), getExpireTime());
            return vObj;
        }
        return JSON.parseObject(vStr, entityClass);
    }
    
    
    public int getExpireTime() {
        return TairConstant.NOT_CARE_EXPIRE;
    }

public class OpserviceImpl implements Opservice \{

@Autowired
    private Operation<List<StudentDo>>      op;
    
    @Override
     public List<StudentDo> getStudents() {
         return op.get("studentKey");
     }

public class StudentDo\{  
private String name;  
private int age;

public String getName()\{  
\}

……代码省略  
\}

如上的代码，类Op继承AbstractOp，再将类Op注入到Opservice中,调用getStudents()方法时得到的是List,解决办法，改造get方法

@Override
    public T get(String customKey) {
        String vStr = CacheUtil.get(getKey(customKey));
        if (null == vStr) {
            T vObj = this.getBizValue();
            CacheUtil.put(getKey(), JSON.toJSONString(vObj, SerializerFeature.WriteClassName), getExpireTime());
            return vObj;
        }
        return (T) JSON.parse(vStr);
    }

注意 这里用的json是fastjson,JSON.toJSONString(vObj, SerializerFeature.WriteClassName)已经对泛型List擦除问题做了处理

[20161108123207619]: /images/20220715/36bc6d1eb94b4e44b86a6a32cb967d3b.png