Question

我正在使用org.springframework.data.jpa.domain.Specification和JpaSpecificationExecutor来轻松创建带有Java条件的查询，但现在我需要调用一个返回整数值的MySQL DB函数。

问题是目前还不清楚如何传递此函数的参数，因为我没有使用TypedQuery：

// cb here is CriteriaBuilder
ParameterExpression param = cb.parameter(String.class);

Predicate predicate = cb.greaterThan(cb.function("A_FUNCTION", 
      Integer.class, param), 0);

Specification spec = cb.and(predicate);

// query is executed like this

return (int) repositoryThatExtendsJpaSpecificationExecutor.count(test);

来自here的示例没有帮助。

Answer 1

我认为您真正需要的是一个可以使用CriteriaBuilder.literal创建的文字。一个完整的例子看起来像

cmake_minimum_required(VERSION 2.8)

# Project
project(005-executable-with-shared-library)

# Directories
set(example_BIN_DIR bin)
set(example_INC_DIR include)
set(example_LIB_DIR lib)
set(example_SRC_DIR src)

# Library files
set(library_SOURCES ${example_SRC_DIR}/library.cpp)
set(library_HEADERS ${example_INC_DIR}/library.h)
set(executable_SOURCES ${example_SRC_DIR}/main.cpp)

# Setting RPATH
# See https://cmake.org/Wiki/CMake_RPATH_handling
set(CMAKE_INSTALL_RPATH ${CMAKE_INSTALL_PREFIX}/${example_LIB_DIR})

# Add library to project
add_library(library SHARED ${library_SOURCES})

# Include directories
target_include_directories(library PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/${example_INC_DIR})

# Add executable to project
add_executable(executable ${executable_SOURCES})

# Linking
target_link_libraries(executable PRIVATE library)

# Install
install(TARGETS executable DESTINATION ${example_BIN_DIR})
install(TARGETS library DESTINATION ${example_LIB_DIR})
install(FILES ${library_HEADERS} DESTINATION ${example_INC_DIR})

如果值不是来自您的应用程序，您可以使用（m）任何functions returning an Expression。

将ParameterExpression与org.springframework.data.jpa.domain.Specification一起使用时如何将参数传递给函数？

1 个答案: