Java 处理“NOT IN（：param）”时的JPA setParameter
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JPA setParameter when dealing with "NOT IN (:param)"
提问by rafa.ferreira
I'm trying to set a parameter in my query, for example:
我正在尝试在我的查询中设置一个参数，例如：
select * from Cars where Cars.color NOT IN (:color_params)
And when I'm adding the parameter in my JavaClass is like:
当我在我的 JavaClass 中添加参数时，就像：
...
query.setParameter("color_params", "RED,BLUE");
...
And this is not working, is only working with only one parameter.
I've tried with "'RED','BLUE'"and is not working to.
这不起作用，仅适用于一个参数。
我已经尝试过，但"'RED','BLUE'"没有成功。
If I put my parameters in the query is working for example:
如果我把我的参数放在查询中，例如：
select * from Cars where Cars.color NOT IN ('RED','BLUE')
What I'm doing wrong!?
我做错了什么！？
Thanks in advance
提前致谢
采纳答案by KLE
You are supposed to pass a List.
你应该通过一个列表。
List<String> colors = ....;
String query = "select * from Cars where Cars.color NOT IN (:color_params)";
Map<String, Object> params = new HashMap<String, Object>();
params.put("color_params", colors);
// ... execute the query with the param.
You could also do:
你也可以这样做：
query.setParameter("color_params", colors);
As a general rule, it is often prefered to pass parameters to a fixed query, instead of customizing the String. The advantages could be:
作为一般规则，通常更喜欢将参数传递给固定查询，而不是自定义字符串。优点可能是：
- Reduced parsing: JPA implementation (at least Hibernate) have a hard work parsing each query. So the parsed query goes into a cache, to be reused. If the query string is build at runtime from parameters, it might never be twice the same, so a lot of time, computing power and cache memory are lost. But if you use the same query string with different parameters, bingo : fast, low memory use, low cpu requirement.
- Prevent SQL injection. This guarantee is offered if you use parameters. If you build your query string with the parameters, you have to provide yourself this guarantee ...!
- 减少解析：JPA 实现（至少是 Hibernate）在解析每个查询时需要付出艰苦的努力。所以解析后的查询进入缓存，以供重用。如果查询字符串是在运行时根据参数构建的，它可能永远不会是相同的两倍，因此会丢失大量时间、计算能力和缓存。但是，如果您使用具有不同参数的相同查询字符串，宾果游戏：速度快，内存使用量低，CPU 要求低。
- 防止 SQL 注入。如果您使用参数，则提供此保证。如果您使用参数构建查询字符串，则必须为自己提供此保证......！
回答by Aaron Digulla
You must pass in a list of strings, not a single string. JPA doesn't parse your values, you must split them yourself.
您必须传入字符串列表，而不是单个字符串。JPA 不解析您的值，您必须自己拆分它们。
