cmake find_package: why cannot find some components in boost - c++

Question

Find_package command is a nightmare to me.
I am trying to include some specified components in boost into my project.
Some components could not be found with find_package command for different error.
Can anyone help to explain the error reported?
case 1:
cmake_minimum_required(VERSION 3.15)
project(tryBoost)
set(CMAKE_CXX_STANDARD 14)
set(BOOST_ROOT "D:\\cygwin64\\home\\yubo\\boost_1_62_0") # either set it here or from the command line
find_package(Boost 1.62.0 REQUIRED COMPONENTS json) # header only libraries must not be added here
add_executable(tryBoost main.cpp)
I try to find json, but error reported：
No header defined for json; skipping header check
case 2:
cmake_minimum_required(VERSION 3.15)
project(tryBoost)
set(CMAKE_CXX_STANDARD 14)
set(BOOST_ROOT "D:\\cygwin64\\home\\yubo\\boost_1_62_0") # either set it here or from the command line
find_package(Boost 1.62.0 REQUIRED COMPONENTS system) # header only libraries must not be added here
add_executable(tryBoost main.cpp)
I try to find system, but error reported：
Could NOT find Boost (missing: Boost_INCLUDE_DIR system)
How boost organizes its components in sub dirs? How find_package command works when scaning boost root dir? why "header only libraries must not be added here".
thanks.

Answer 1

Please use below CMakeList.txt for reference.
cmake_minimum_required(VERSION 3.15)
project(tryBoost)
set(CMAKE_CXX_STANDARD 14)
#set(Boost_DEBUG ON)
set(Boost_USE_STATIC_LIBS ON)
set(Boost_USE_MULTITHREADED ON)
set(BOOST_ROOT "/home/yubo/boost_1_78_0")
add_executable(tryBoost main.cpp)
set(Boost_NO_BOOST_CMAKE FALSE CACHE BOOL "" FORCE)
find_package(Boost 1.78.0 REQUIRED COMPONENTS json)
message("${Boost_FOUND}")
message("Boost_INCLUDE_DIRS: ${Boost_INCLUDE_DIRS}")
target_include_directories(tryBoost PUBLIC ${Boost_INCLUDE_DIRS})
message("Boost_LIBRARY_DIRS: ${Boost_LIBRARY_DIRS}")
message("Boost_LIBRARIES: ${Boost_LIBRARIES}")
target_link_libraries(tryBoost ${Boost_LIBRARIES})