blocks|key|1749161|text|这个问题已经提出很长一段时间了，但我希望我的答案能对像我这样的人有所帮助。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1749162|如果您查看一下javax.persistence+api+docs，您将看到自Java+Persistence+2.0以来已经在其中添加了一些新方法。其中之一是返回TypedQuery<T>的createQuery(String,+Class<T>)。您可以像使用Query一样使用TypedQuery，但稍有不同的是，现在所有操作都是类型安全的。|offset|length|style|CODE|1749163|因此，只需将您的代码更改为smth，如下所示：|1749164|Query+q+=+sess.createQuery("from+Cat+cat",+Cat.class);
List<Cat>+cats+=+q.list();|code-block|syntax|javascript|1749165|你已经准备好了。|1749166|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javaee/6/api/javax/persistence/EntityManager.html#createQuery(java.lang.String,%2520java.lang.Class))^0|0|13|K|2A|D|2O|T|3O|5|3X|A|P|8|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@$D|10|E|11|F|G]|$D|12|E|13|F|G]|$D|14|E|15|F|G]|$D|16|E|17|F|G]|$D|18|E|19|F|G]]|9|@$D|1A|E|1B|1|1C]]|A|$]]|$1|H|3|I|5|6|7|1D|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|1E|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|1F|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]]]

It is been a long time since the question was asked but I hope my answer might be helpful to someone like me.

If you take a look at javax.persistence <a href="http://docs.oracle.com/javaee/6/api/javax/persistence/EntityManager.html#createQuery(java.lang.String,%20java.lang.Class)">api docs</a>, you will see that some new methods have been added there since <code>Java Persistence 2.0</code>. One of them is <code>createQuery(String, Class&lt;T&gt;)</code> which returns <code>TypedQuery&lt;T&gt;</code>. You can use <code>TypedQuery</code> just as you did it with <code>Query</code> with that small difference that all operations are type safe now.

So, just change your code to smth like this:

<pre><code>Query q = sess.createQuery("from Cat cat", Cat.class);
List&lt;Cat&gt; cats = q.list();
</code></pre>

And you are all set.

blocks|key|1533971|text|我们也使用@SuppressWarnings("unchecked")，但我们通常只在变量的声明上使用它，而不是在整个方法上使用它：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1533972|public+List<Cat>+findAll()+{
++++Query+q+=+sess.createQuery("from+Cat+cat");
++++@SuppressWarnings("unchecked")
++++List<Cat>+cats+=+q.list();
++++return+cats;
}|code-block|syntax|javascript|1533973|entityMap^0|5|U|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

We use <code>@SuppressWarnings("unchecked")</code> as well, but we most often try to use it only on the declaration of the variable, not on the method as a whole:

<pre><code>public List&lt;Cat&gt; findAll() {
 Query q = sess.createQuery("from Cat cat");
 @SuppressWarnings("unchecked")
 List&lt;Cat&gt; cats = q.list();
 return cats;
}
</code></pre>

blocks|key|1534309|text|尝试使用TypedQuery而不是Query。例如，不是这样：-|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1534310|Query+q+=+sess.createQuery("from+Cat+cat",+Cat.class);
List<Cat>+cats+=+q.list();|code-block|syntax|javascript|1534311|使用这个：-|1534312|TypedQuery<Cat>+q1+=+sess.createQuery("from+Cat+cat",+Cat.class);
List<Cat>+cats+=+q1.list();|1534313|entityMap^0|4|A|H|5|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

Try to use <code>TypedQuery</code> instead of <code>Query</code>.
For example instead of this:-

<pre><code>Query q = sess.createQuery("from Cat cat", Cat.class);
List&lt;Cat&gt; cats = q.list();
</code></pre>

Use this:-

<pre><code>TypedQuery&lt;Cat&gt; q1 = sess.createQuery("from Cat cat", Cat.class);
List&lt;Cat&gt; cats = q1.list();
</code></pre>

blocks|key|1533760|text|在我们的代码中，我们使用以下注释来注释调用方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1533761|@SuppressWarning(“未勾选”)|1533762|我知道这看起来像是黑客攻击，但是一个联合开发人员最近检查了一下，发现这是我们唯一能做的。|1533763|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

In our code we annotate the calling methods with:

@SuppressWarnings("unchecked")

I know it seems like a hack, but a co-developer checked recently and found that was all we could do.

blocks|key|1534047|text|这不是疏忽也不是错误。这个警告反映了一个真正的潜在问题--+java编译器不可能真正确保hibernate类能够正确地完成它的工作，并且它返回的列表将只包含Cat。这里的任何建议都是好的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1534048|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

It's not an oversight or a mistake. The warning reflects a real underlying problem - there is no way that the java compiler can really be sure that the hibernate class is going to do it's job properly and that the list it returns will only contain Cats. Any of the suggestions here is fine.

blocks|key|1533828|text|不能，但您可以将其隔离到特定的查询方法中，并使用@SuppressWarnings("unchecked")注释隐藏警告。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1533829|entityMap^0|O|U|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

No, but you can isolate it into specific query methods and suppress the warnings with a <code>@SuppressWarnings("unchecked")</code> annotation.

blocks|key|1749315|text|Hibernate的较新版本现在支持类型安全的Query<T>对象，因此您不再需要使用@SuppressWarnings或实现一些hack来消除编译器警告。在Session+API中，Session.createQuery现在将返回一个类型安全的Query<T>对象。您可以这样使用它：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1749316|Query<Cat>+query+=+session.createQuery("FROM+Cat",+Cat.class);
List<Cat>+cats+=+query.list();|code-block|syntax|javascript|1749317|当查询结果不返回Cat时，也可以使用它：|1749318|public+Integer+count()+{
++++Query<Integer>+query+=+sessionFactory.getCurrentSession().createQuery("SELECT+COUNT(id)+FROM+Cat",+Integer.class);
++++return+query.getSingleResult();
}|1749319|或者在执行部分选择时：|1749320|public+List<Object[]>+String+getName()+{
++++Query<Object[]>+query+=+sessionFactory.getCurrentSession().createQuery("SELECT+id,+name+FROM+Cat",+Object[].class);
++++return+query.list();
}|1749321|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.jboss.org/hibernate/orm/5.2/javadocs/org/hibernate/Session.html#createQuery-java.lang.String-java.lang.Class-^0|N|8|17|H|2K|J|3F|8|27|B|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@$9|19|A|1A|1|1B]]|E|$]]|$1|F|3|G|5|H|7|1C|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1D|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|1E|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1F|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1G|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|1H|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]]]

Newer versions of Hibernate now support a type safe <code>Query&lt;T&gt;</code> object so you no longer have to use <code>@SuppressWarnings</code> or implement some hack to make the compiler warnings go away. In the <a href="https://docs.jboss.org/hibernate/orm/5.2/javadocs/org/hibernate/Session.html#createQuery-java.lang.String-java.lang.Class-" rel="nofollow noreferrer">Session API</a>, <code>Session.createQuery</code> will now return a type safe <code>Query&lt;T&gt;</code> object. You can use it this way:

<pre><code>Query&lt;Cat&gt; query = session.createQuery("FROM Cat", Cat.class);
List&lt;Cat&gt; cats = query.list();
</code></pre>

You can also use it when the query result won't return a Cat:

<pre><code>public Integer count() {
 Query&lt;Integer&gt; query = sessionFactory.getCurrentSession().createQuery("SELECT COUNT(id) FROM Cat", Integer.class);
 return query.getSingleResult();
}
</code></pre>

Or when doing a partial select:

<pre><code>public List&lt;Object[]&gt; String getName() {
 Query&lt;Object[]&gt; query = sessionFactory.getCurrentSession().createQuery("SELECT id, name FROM Cat", Object[].class);
 return query.list();
}
</code></pre>

blocks|key|1749052|text|我知道这是较老的，但有两点要注意，今天在马特奎尔斯的答案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1749053|第1点|1749054|这|1749055|List<Cat>+cats+=+Collections.checkedList(Cat.class,+q.list());|code-block|syntax|javascript|1749056|应该是这样的|1749057|List<Cat>+cats+=+Collections.checkedList(q.list(),+Cat.class);|1749058|第2点|1749059|从这里开始|1749060|List+list+=+q.list();|1749061|到这个|1749062|List<T>+list+=+q.list();|1749063|将明显减少浏览器剥离的原始回复标签标记中的其他警告。|1749064|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|14|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|15|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|16|8|@]|9|@]|A|$]]|$1|M|3|N|5|H|7|17|8|@]|9|@]|A|$I|J]]|$1|O|3|P|5|6|7|18|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|19|8|@]|9|@]|A|$]]|$1|S|3|T|5|H|7|1A|8|@]|9|@]|A|$I|J]]|$1|U|3|V|5|6|7|1B|8|@]|9|@]|A|$]]|$1|W|3|X|5|H|7|1C|8|@]|9|@]|A|$I|J]]|$1|Y|3|Z|5|6|7|1D|8|@]|9|@]|A|$]]|$1|10|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]]|11|$]]

I know this is older but 2 points to note as of today in Matt Quails Answer.

<h1>Point 1</h1>

This 

<pre><code>List&lt;Cat&gt; cats = Collections.checkedList(Cat.class, q.list());
</code></pre>

Should be this

<pre><code>List&lt;Cat&gt; cats = Collections.checkedList(q.list(), Cat.class);
</code></pre>

<h1>Point 2</h1>

From this

<pre><code>List list = q.list();
</code></pre>

to this 

<pre><code>List&lt;T&gt; list = q.list();
</code></pre>

would reduce other warnings obviously in original reply tag markers were stripped by the browser.

blocks|key|1534162|text|试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1534163|Query+q+=+sess.createQuery("from+Cat+cat");
List<?>+results+=+q.list();
for+(Object+obj+:+results)+{
++++Cat+cat+=+(Cat)+obj;
}|code-block|syntax|javascript|1534164|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try this:

<pre><code>Query q = sess.createQuery("from Cat cat");
List&lt;?&gt; results = q.list();
for (Object obj : results) {
 Cat cat = (Cat) obj;
}
</code></pre>

blocks|key|1749225|text|使用hibernate+query避免类型安全警告的一个很好的解决方案是使用像TorpedoQuery这样的工具来帮助您构建类型安全的hql。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1749226|Cat+cat+=+from(Cat.class);
org.torpedoquery.jpa.Query<Entity>+select+=+select(cat);
List<Cat>+cats+=+select.list(entityManager);|code-block|syntax|javascript|1749227|entityMap|0|LINK|mutability|MUTABLE|url|http://torpedoquery.org/^0|13|C|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

A good solution to avoid type safety warnings with hibernate query is to use a tool like <a href="http://torpedoquery.org" rel="nofollow">TorpedoQuery</a> to help you to build type safe hql.

<pre><code>Cat cat = from(Cat.class);
org.torpedoquery.jpa.Query&lt;Entity&gt; select = select(cat);
List&lt;Cat&gt; cats = select.list(entityManager);
</code></pre>

blocks|key|1749338|text|TypedQuery<EntityName>+createQuery+=+entityManager.createQuery("from+EntityName",+EntityName.class);
List<EntityName>+resultList+=+createQuery.getResultList();|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1749339|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>TypedQuery&lt;EntityName&gt; createQuery = entityManager.createQuery("from EntityName", EntityName.class);
List&lt;EntityName&gt; resultList = createQuery.getResultList();
</code></pre>

blocks|key|1533901|text|如果你不想使用@SuppressWarning(“未选中”)，你可以执行以下操作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1533902|+++Query+q+=+sess.createQuery("from+Cat+cat");
+++List<?>+results+=(List<?>)+q.list();
+++List<Cat>+cats+=+new+ArrayList<Cat>();
+++for(Object+result:results)+{
+++++++Cat+cat+=+(Cat)+result;
+++++++cats.add(cat);
++++}|code-block|syntax|javascript|1533903|仅供参考-我创建了一个util方法来为我做这件事，这样它就不会弄乱我的代码，我也不需要使用@SupressWarning。|1533904|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

If you don't want to use @SuppressWarnings("unchecked") you can do the following.

<pre><code> Query q = sess.createQuery("from Cat cat");
 List&lt;?&gt; results =(List&lt;?&gt;) q.list();
 List&lt;Cat&gt; cats = new ArrayList&lt;Cat&gt;();
 for(Object result:results) {
 Cat cat = (Cat) result;
 cats.add(cat);
 }
</code></pre>

FYI - I created a util method that does this for me so it doesn't litter my code and I don't have to use @SupressWarning.

For example I have such query:

<pre><code>Query q = sess.createQuery("from Cat cat");
List cats = q.list();
</code></pre>

If I try to make something like this it shows the following warning 

<pre><code>Type safety: The expression of type List needs unchecked conversion to conform to List&lt;Cat&gt;


List&lt;Cat&gt; cats = q.list();
</code></pre>

Is there a way to avoid it?

How to avoid type safety warnings with Hibernate HQL results?

编译器

Java

例如，我有这样的查询：Query q = sess.createQuery("from Cat cat");List cats = q.list();如果我尝试这样做，它会显示以下警告Type safety: The expression of type List needs unchecked conversion to conform to List<Cat>List<Cat> cats =

问如何避免Hibernate HQL结果的类型安全警告？
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回答 12

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问如何避免Hibernate HQL结果的类型安全警告？
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