About the problems encountered by mapStruct in converting List objects

Problem Description

During project development, object conversion was used mapStruct, Listand the parameters in the object changed. @MapingAnnotations were used, and it was found that the converted parameters were not converted, and the content was null.

    @Mapping(source = "jsid", target = "id")
    @Mapping(source = "roleGroupId", target = "pid")
    List<SystemRoleCO> toListSystemRoleCO(List<UserRoleDO> userRoleDOS);

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Cause Analysis:

Clicking on the implementation class method found that the attribute to be converted was not generated. A colleague pointed out that it may be necessary to have a conversion method for this object first, which is strange.

       protected SystemRoleCO userRoleDOToSystemRoleCO(UserRoleDO userRoleDO) {
    
    
        if ( userRoleDO == null ) {
    
    
            return null;
        }

        SystemRoleCO systemRoleCO = new SystemRoleCO();

        systemRoleCO.setJsmc( userRoleDO.getJsmc() );
        systemRoleCO.setJsjb( userRoleDO.getJsjb() );

        return systemRoleCO;
    }

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solution:

Define an object before definition List<对象>and the conversion will be successful.

    @Mapping(source = "jsid", target = "id")
    @Mapping(source = "roleGroupId", target = "pid")
    SystemRoleCO toListSystemRoleCO(UserRoleDO userRoleDOS);

    @Mapping(source = "jsid", target = "id")
    @Mapping(source = "roleGroupId", target = "pid")
    List<SystemRoleCO> toListSystemRoleCO(List<UserRoleDO> userRoleDOS);