将 TIMESTAMPDIFF 与 JPA 条件查询和休眠作为提供者一起使用

Question

我有一个数据表，其中包含 setup 和 release 列，两者都包含时间戳。我的目标是使用 CriteriaQuery 创建下面的 SQL 查询的等效项。

SQL查询：SELECT TIMESTAMPDIFF(SECOND, setup, released)) as sum_duration FROM calls

CriteriaBuilder#diff() 函数显然不起作用，因为它需要数字参数，所以我尝试使用 CriteriaBuilder#function：

EntityManager entityManager = emProvider.get();

CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();

CriteriaQuery<Integer> query = criteriaBuilder.createQuery();

Root<Thingy> thingyRoot = query.from(Thingy.class);

Path<DateTime> setup = root.get("setup");
Path<DateTime> release = root.get("release");

Expression secondLiteral = criteriaBuilder.literal("SECOND");

Expression func = criteriaBuilder.function("TIMESTAMPDIFF", Integer.class, secondLiteral, setup, release);

entityManager.createQuery(query).getResultList();

但是，当我尝试运行此代码时，它引发了异常；看来文字没有呈现为常量，而是呈现为参数：

java.lang.IllegalStateException: No data type for node: org.hibernate.hql.internal.ast.tree.MethodNode 
 \-[METHOD_CALL] MethodNode: '('
    +-[METHOD_NAME] IdentNode: 'TIMESTAMPDIFF' {originalText=TIMESTAMPDIFF}
    \-[EXPR_LIST] SqlNode: 'exprList'
       +-[NAMED_PARAM] ParameterNode: '?' {name=param0, expectedType=null}
       +-[DOT] DotNode: 'cdr0_.setup' {propertyName=setup,dereferenceType=ALL,propertyPath=setup,path=generatedAlias0.setup,tableAlias=cdr0_,className=com.vtsl.domain.CDR,classAlias=generatedAlias0}
       |  +-[ALIAS_REF] IdentNode: 'cdr0_.id' {alias=generatedAlias0, className=com.vtsl.domain.CDR, tableAlias=cdr0_}
       |  \-[IDENT] IdentNode: 'setup' {originalText=setup}
       \-[DOT] DotNode: 'cdr0_.release' {propertyName=release,dereferenceType=ALL,propertyPath=release,path=generatedAlias0.release,tableAlias=cdr0_,className=com.vtsl.domain.CDR,classAlias=generatedAlias0}
          +-[ALIAS_REF] IdentNode: 'cdr0_.id' {alias=generatedAlias0, className=com.vtsl.domain.CDR, tableAlias=cdr0_}
          \-[IDENT] IdentNode: 'release' {originalText=release}

所以我尝试匿名覆盖LiteralExpression#render 以直接返回我提供给该方法的字符串，但是出现了这个异常。

java.lang.IllegalStateException: No data type for node: org.hibernate.hql.internal.ast.tree.MethodNode 
 \-[METHOD_CALL] MethodNode: '('
    +-[METHOD_NAME] IdentNode: 'TIMESTAMPDIFF' {originalText=TIMESTAMPDIFF}
    \-[EXPR_LIST] SqlNode: 'exprList'
       +-[IDENT] IdentNode: 'SECOND' {originalText=SECOND}
       +-[DOT] DotNode: 'cdr0_.setup' {propertyName=setup,dereferenceType=ALL,propertyPath=setup,path=generatedAlias0.setup,tableAlias=cdr0_,className=com.vtsl.domain.CDR,classAlias=generatedAlias0}
       |  +-[ALIAS_REF] IdentNode: 'cdr0_.id' {alias=generatedAlias0, className=com.vtsl.domain.CDR, tableAlias=cdr0_}
       |  \-[IDENT] IdentNode: 'setup' {originalText=setup}
       \-[DOT] DotNode: 'cdr0_.release' {propertyName=release,dereferenceType=ALL,propertyPath=release,path=generatedAlias0.release,tableAlias=cdr0_,className=com.vtsl.domain.CDR,classAlias=generatedAlias0}
          +-[ALIAS_REF] IdentNode: 'cdr0_.id' {alias=generatedAlias0, className=com.vtsl.domain.CDR, tableAlias=cdr0_}
          \-[IDENT] IdentNode: 'release' {originalText=release}

所以问题是：我怎样才能修复我正在尝试做的这个操作，或者实现最初的目标？

我正在使用 Hibernate，我的数据库是 MySQL。

Answer 1

这里有一个比 Kalid Shah 的更通用的解决方案。

基本上，我们需要的是一个自定义的“不透明文字”Expression 类，它能够将任意标记表达式（如MONTH、YEAR、INTERVAL 1 DAY 等）作为函数参数传递给 MySQL：

import javax.persistence.criteria.CriteriaBuilder;

import org.hibernate.query.criteria.internal.CriteriaBuilderImpl;
import org.hibernate.query.criteria.internal.compile.RenderingContext;
import org.hibernate.query.criteria.internal.expression.LiteralExpression;

/**
 * Represents an opaque literal that gets pass through JPA unaltered into SQL.
 */
@SuppressWarnings("serial")
public class OpaqueLiteralExpression extends LiteralExpression<Void> {

    private final String value;

    public OpaqueLiteralExpression(CriteriaBuilderImpl builder, String value) {
        super(builder, Void.class, null);
        if (value == null)
            throw new IllegalArgumentException("null value");
        this.value = value;
    }

// ExpressionImpl

    @Override
    public String render(RenderingContext renderingContext) {
        return this.value;
    }
}

那么你可以这样使用它：

final Expression<LocalDate> birthDate = student.get(Student_.birthDate);
final Expression<Integer> age = builder.function("TIMESTAMPDIFF", Integer.class,
  new OpaqueLiteralExpression(builder, "YEAR"), birthDate, LocalDate.now());

Answer 2

CASE WHEN 1=1 THEN TIMESTAMPDIFF(SECOND,startDatetime,endDatetime) ELSE 0 END

用 case 语句模拟它。

Answer 3

这里是对等价的JPA Criteria Query的解释

SELECT * from calls where TIMESTAMPDIFF(SECOND, setup, released)

首先，您必须创建单位表达式并从BasicFunctionExpression 扩展它，其中以“SECOND”参数为单位并仅覆盖其rendor(RenderingContext renderingContext) 方法。

import java.io.Serializable;
import org.hibernate.query.criteria.internal.CriteriaBuilderImpl;
import org.hibernate.query.criteria.internal.compile.RenderingContext;
import org.hibernate.query.criteria.internal.expression.function.BasicFunctionExpression;

public class UnitExpression extends BasicFunctionExpression<String> implements Serializable {

  public UnitExpression(CriteriaBuilderImpl criteriaBuilder, Class<String> javaType,
      String functionName) {
    super(criteriaBuilder, javaType, functionName);
  }

  @Override
  public String render(RenderingContext renderingContext) {
    return getFunctionName();
  }
}

然后你在你的 JPA 条件查询中使用这个单位表达式。

EntityManager entityManager = emProvider.get();
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
Root<Calls> thingyRoot = query.from(Calls.class);

    Expression<String> second = new UnitExpression(null, String.class, "SECOND");
    Expression<Integer> timeInSec = cb.function(
        "TIMESTAMPDIFF",
        Integer.class,
        second ,
        root.<Timestamp>get("setup"),
        root.<Timestamp>get("release"));
    List<Predicate> conditions = new ArrayList<>();
    conditions.add(cb.lessThan(timeInSec, 3600));
    cq.where(conditions.toArray(new Predicate[]{}));
    return session.createQuery(cq);

它正在工作。

Answer 4

我遇到了同样的问题：SECOND 将被撇号包围，查询将引发异常。

我通过以下代码解决了这个问题：

CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<MyEntity> cq = builder.createQuery( MyEntity.class );
Root<MyEntity> root = cq.from( MyEntity.class );

javax.persistence.criteria.Expression<java.sql.Time> timeDiff = builder.function(
            "TIMEDIFF",
            java.sql.Time.class,
            root.<Date>get( "endDate" ),
            root.<Date>get( "startDate" ) );
javax.persistence.criteria.Expression<Integer> timeToSec = builder.function(
            "TIME_TO_SEC",
            Integer.class,
            timeDiff );

//lessThanOrEqualTo 60 minutes
cq.where( builder.lessThanOrEqualTo( timeToSec, 3600 ) );

return em.createQuery( cq ).getResultList();

这给了我同样的结果。