demo shiny server app with health handler returning plain json on health path

shiny_dummy_json_health.R

#
# This is a Shiny web application. 
# with a handler that returns plain json
# run and in a browser look for /health/
# e.g. http://127.0.0.1:5732/health/
# from https://stackoverflow.com/users/1455889/amaurel
# on https://stackoverflow.com/questions/19991654/shiny-server-print-json-as-a-result-output
# You can run the application by clicking
# the 'Run App' button above.
#
# Find out more about building applications with Shiny here:
#
#    http://shiny.rstudio.com/
#

library(shiny)
library(jsonlite)

# Define UI for application that draws a histogram
ui <- fluidPage(

    # Application title
    titlePanel("Old Faithful Geyser Data"),

    # Sidebar with a slider input for number of bins 
    sidebarLayout(
        sidebarPanel(
            sliderInput("bins",
                        "Number of bins:",
                        min = 1,
                        max = 50,
                        value = 30)
        ),

        # Show a plot of the generated distribution
        mainPanel(
           plotOutput("distPlot")
        )
    )
)

httpHandler = function(req){
    message = list(value="hello")
    return(list(status = 200L,
                headers = list('Content-Type' = 'application/json'),
                body = toJSON(message)))
}
shiny:::handlerManager$addHandler(shiny:::routeHandler("/health",httpHandler) , "a_unique_id")

# Define server logic required to draw a histogram
server <- function(input, output) {

    output$distPlot <- renderPlot({
        # generate bins based on input$bins from ui.R
        x    <- faithful[, 2]
        bins <- seq(min(x), max(x), length.out = input$bins + 1)

        # draw the histogram with the specified number of bins
        hist(x, breaks = bins, col = 'darkgray', border = 'white')
    })
}

# Run the application 
shinyApp(ui = ui, server = server)

Thanks for letting me know.