HQL：可变列 [英] HQL: variable column

问题描述

  Query criteria = session.createQuery（
select test.col1，test.col2，test.col3 
from Test test+ 
where test.col =：variableValue）; 
 criteria.setInteger（variableValue ，10）; 
  

但是可以像这样设置变量列吗？

 字符串variableColumn =test.col1; 
 Query criteria = session.createQuery（
select test.col1，test .col2，test.col3 
from Test test+ 
其中：variableColumn =：variableValue）; 
 criteria.setInteger（variableValue，10）; 
 criteria.setString（variableColumn，variableColumn）; 
  

这是结果：

 线程main中的异常Hibernate：select .... where？=？ ... 
 org.hibernate.exception.SQLGrammarException：无法在org.hibernate.exception.SQLStateConverter.convert（SQLStateConverter.java:92）
 ... $ b $执行查询
 b在_test.TestCriteria.main（TestCriteria.java:44）
导致：com.microsoft.sqlserver.jdbc.SQLServerException：将nvarchar值'test.col1'转换为数据类型int时转换失败。 
 ... 
  

更新（工作解决方案）：

 查询条件= session.createQuery（
select test.col1，test.col2，test.col3 $ b $ 
其中（：value1为null或test.col1 =：value1）AND 
（：value2为null或test.col2 =：value2）
  

解决方案

这在您的应用程序中有意义吗？

  String test =select test.col1，test.col2，test.col3+ 
from Test test+ 
where {columnName} =：variableValue; 
 Object variableValue = //从某处获取
 String columnName = //另一个从某处获取
 query = query.replace（{columnName}，columName ）; 
 //现在继续照常
  

这通常是一个 naive 查询构造函数您可能需要将此想法重构为一个单独的基于实用程序/实体的类来完善（例如S QL注入）执行前的查询。

I'm able to set variable values for "where" restrictives:

Query criteria = session.createQuery(
  "select test.col1, test.col2, test.col3
  "from Test test " +
  "where test.col = :variableValue ");
criteria.setInteger("variableValue", 10);

But is it possible to set variable column like this?

String variableColumn = "test.col1";
Query criteria = session.createQuery(
  "select test.col1, test.col2, test.col3
  "from Test test " +
  "where :variableColumn = :variableValue ");
criteria.setInteger("variableValue", 10);
criteria.setString("variableColumn", variableColumn);

This is the result:

Exception in thread "main" Hibernate: select .... where ?=? ...
org.hibernate.exception.SQLGrammarException: could not execute query
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:92)
    ...
    at _test.TestCriteria.main(TestCriteria.java:44)
Caused by: com.microsoft.sqlserver.jdbc.SQLServerException: Conversion failed when converting the nvarchar value 'test.col1' to data type int.
    ...

UPDATE (working solution):

Query criteria = session.createQuery(
  "select test.col1, test.col2, test.col3
  "from Test test " +
  "where (:value1 is null OR test.col1 = :value1) AND 
         (:value2 is null OR test.col2 = :value2) "

解决方案

Does this make sense in your application:

String query =  "select test.col1, test.col2, test.col3" + 
  "from Test test " +
  "where {columnName} = :variableValue ";
Object variableValue = // retrieve from somewhere
String columnName = // another retrieve from somewhere
query = query.replace("{columnName}", columName);
// Now continue as always

This is generally a naive query constructor. You may need to refactor this idea to a separate utility/entity-based class to refine (e.g. SQL injection) the queries before execution.

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