apache/dolphinscheduler · error

PROJECT_PARAMETER_ALREADY_EXISTS

PROJECT_PARAMETER_ALREADY_EXISTS

Error message

ProjectParameter {} already exists.

What it means

createProjectParameter returns PROJECT_PARAMETER_ALREADY_EXISTS when a ProjectParameter row with the same projectCode and paramName already exists. Parameter names must be unique within a project, so duplicate creation is rejected.

Source

Thrown at dolphinscheduler-api/src/main/java/org/apache/dolphinscheduler/api/service/impl/ProjectParameterServiceImpl.java:85

    @Override
    @Transactional
    public Result createProjectParameter(User loginUser, long projectCode, String projectParameterName,
                                         String projectParameterValue, String projectParameterDataType) {
        Result result = new Result();

        // check if user have write perm for project
        Project project = projectDao.queryByCode(projectCode);
        projectService.checkHasProjectWritePermissionThrowException(loginUser, project);

        // check if project parameter name exists
        ProjectParameter projectParameter = projectParameterMapper.selectOne(new QueryWrapper<ProjectParameter>()
                .lambda()
                .eq(ProjectParameter::getProjectCode, projectCode)
                .eq(ProjectParameter::getParamName, projectParameterName));

        if (projectParameter != null) {
            log.warn("ProjectParameter {} already exists.", projectParameter.getParamName());
            putMsg(result, Status.PROJECT_PARAMETER_ALREADY_EXISTS, projectParameter.getParamName());
            return result;
        }

        Date now = new Date();

        projectParameter = ProjectParameter
                .builder()
                .paramName(projectParameterName)
                .paramValue(projectParameterValue)
                .paramDataType(projectParameterDataType)
                .code(CodeGenerateUtils.genCode())
                .projectCode(projectCode)
                .userId(loginUser.getId())
                .operator(loginUser.getId())
                .createTime(now)
                .updateTime(now)
                .build();

View on GitHub (pinned to 02eac45a1b)

Solutions

  1. Use the update (PUT /project-parameter) endpoint instead of create to change an existing parameter's value.
  2. Rename the new parameter to a unique name within the project.
  3. Query existing parameters first (GET /project-parameter/list) and skip creation if present.

Example fix

// before
service.createProjectParameter(user, code, "jdbc.url", "jdbc:..."); // fails if exists
// after
if (projectParameterService.listProjectParameter(user, code, "jdbc.url", 1, 10).getResult() == null) {
    service.createProjectParameter(user, code, "jdbc.url", "jdbc:...");
}
Defensive patterns

Strategy: try-catch

Validate before calling

long existing = projectParameterMapper.selectCount(new LambdaQueryWrapper<ProjectParameter>()
        .eq(ProjectParameter::getProjectCode, code)
        .eq(ProjectParameter::getParamName, name));
if (existing > 0) { /* update instead of create */ }

Try / catch

catch (ServiceException e) { if (e.getCode() == Status.PROJECT_PARAMETER_ALREADY_EXISTS) { /* fall back to update */ } }

Prevention

When it happens

Trigger: POST /project-parameter with a paramName that already exists in the given projectCode, e.g. creating parameter 'jdbc.url' twice in the same project.

Common situations: Re-submitting a create form after a previous successful save; automation scripts creating parameters idempotently; user typing a name that collides with an existing parameter.

Understand the failure class

Background: "already exists" / EEXIST / FileAlreadyExistsException: what the 'file already exists' error means and how to fix it — this error's family across 37 libraries.

Related errors

AI-assisted analysis of apache/dolphinscheduler@02eac45a1b (2026-09-06). Data as JSON: /api/errors/3789447b32c8531d. Report an issue: GitHub.