Using `respond` with a custom model name

[bessb]

It appears that if I use respond then the model name is determined by the type e.g.

class HelloController  {

    static responseFormats = ['json']

    def test() {
        def messages = [
            [hello: 'world'],
            [foo: 'bar']
        ]
        respond messages
    }
}

My view has to look like this:

model {
    List linkedHashMapList
}
json {
    messages linkedHashMapList
}

If I don't use respond, and simply return a Map from my action, then I can use whatever model name I want in my view:

class HelloController  {

    static responseFormats = ['json']

    def test() {
        def messages = [
            [hello: 'world'],
            [foo: 'bar']
        ]
        [messages: messages]
    }
}

model {
    List messages
}
json {
    messages messages
}

Is there a way to use respond and use a custom name for the model? It appears that passing a model argument to respond does not work, it still uses the name determined by type.

[jameskleeh]

@bessb Why is using the map style syntax not a viable alternative for you?

[bessb]

The map style syntax is fine in this case, but I tend to use respond in most cases to simplify content negotiation.

[nikhilsharma8193]

I am not able to use respond() for maps. It always returns {} empty JSON object.
It works with render but then the MongoDB ObjectId is rendered as an object instead of it's toString() value i.e hex string representation.

Without having a dedicated view file, it uses the _object.gson to render the map but then I have to remove the g.render() call.

model {
    Object object
}

json object

But in this case also it is not able to render lists and maps. Though it renders correctly if I pass a string value like respond([hi: 'hello']) it responds as,

{
  "hi": "hello"
}

[nikhilsharma8193]

@bessb

So I finally found a workaround that lets me use the default _object.gson file for rendering maps, lists and domain instances without having to create a dedicated view file for each action in my controller.

The workaround only works with static compilation disabled which will affect performance as per the docs. So if anyone has a better solution, please share.

In application.groovy:

grails.views.json.compileStatic = false

Replace default _object.gson with this code :

import grails.artefact.DomainClass
import grails.plugin.json.builder.JsonOutput

model {
    Object object
}

def getJsonValue(def valueToJson) {
    if (valueToJson instanceof Map) {
        Map renderedValueMap = [:]

        valueToJson.each { key, value ->
            def valueToBeRendered
            if (value instanceof String) {
                valueToBeRendered = value
            } else {
                valueToBeRendered = getJsonValue(value)

                if (valueToBeRendered instanceof CharSequence) {
                    valueToBeRendered = JsonOutput.unescaped(valueToBeRendered)
                }
            }

            renderedValueMap.put("$key", valueToBeRendered)
        }

        return renderedValueMap
    }

    if (valueToJson instanceof Iterable) {
        List renderedValueList = []

        valueToJson.each { value ->
            renderedValueList.add(getJsonValue(value))
        }

        return renderedValueList
    } else if (valueToJson instanceof DomainClass) {
        return g.render(valueToJson)
    } else {
        return valueToJson
    }
}

if (object instanceof Map) {
    json {
        object.each { key ,value ->
            "$key" getJsonValue(value)
        }
    }
} else if (object instanceof List) {
    json getJsonValue(object)
} else {
    json g.render(object)
}

[vmptk]

How did you resolve this?
1 error
] with root cause
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
admin_command_execute_gson: 42: [Static type checking] - cannot resolve dynamic method name at compile time.
@ line 42, column 13.
"${entry.key}" getJsonValue(entry.value)
^

1 error

at org.codehaus.groovy.control.ErrorCollector.failIfErrors(ErrorCollector.java:310)
at org.codehaus.groovy.control.CompilationUnit.applyToPrimaryClassNodes(CompilationUnit.java:1073)
at org.codehaus.groovy.control.CompilationUnit.doPhaseOperation(CompilationUnit.java:591)
at org.codehaus.groovy.control.CompilationUnit.processPhaseOperations(CompilationUnit.java:569)
at org.codehaus.groovy.control.CompilationUnit.compile(CompilationUnit.java:546)
at groovy.lang.GroovyClassLoader.doParseClass(GroovyClassLoader.java:298)
at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:268)
at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:254)
at grails.views.ResolvableGroovyTemplateEngine$_createTemplate_closure2.doCall(ResolvableGroovyTemplateEngine.groovy:391)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)

[nikhilsharma8193]

@VenelinPetkov
You need to disable static compilation for gson views. I already mentioned that in my post.

[vmptk]

@nikhilsharma8193 Thanks, just seen it.... I still get null when trying to respond a map. What are you returning from the controller?

[nikhilsharma8193]

@VenelinPetkov

Please show example response that is failing. I am able to respond lists, maps and object instances.

Note: This workaround is for using respond.

Are you simply returning the map ? If so, it won't work. It should be respond(yourMapHere).

[vmptk]

@nikhilsharma8193 Here it is:
Controller:

class CommandController {
    static allowedMethods = [execute: "POST"]

    CommandService commandService

    def execute() {
        log.debug "uri: '${actionUri}', params: '${params}'"
        def data = request?.JSON
        log.debug "Request data: ${data}"
        Map executeResult = [:]
        task {
            executeResult = commandService.compose()
            log.debug "result[${executeResult.size()}]"
            def result = [[object: executeResult]]
            respond result, [formats: ['xml','json']]
        }
    }
}

I have tried both ways to specify the return with/without respond and formats and directly list of map

JSONView (same as yours):

import admin.Batches
import grails.plugin.json.builder.JsonOutput

model {
    Object object
}

def getJsonValue(def valueToJson) {
    if (valueToJson instanceof Map) {
        Map renderedValueMap = [:]
        valueToJson.each { key, value ->
            def valueToBeRendered
            if (value instanceof String) {
                valueToBeRendered = value
            } else {
                valueToBeRendered = getJsonValue(value)
                if (valueToBeRendered instanceof CharSequence) {
                    valueToBeRendered = JsonOutput.unescaped(valueToBeRendered)
                }
            }
            renderedValueMap.put("$key", valueToBeRendered)
        }
        return renderedValueMap
    }

    if (valueToJson instanceof Iterable) {
        List renderedValueList = []
        valueToJson.each { value ->
            renderedValueList.add(getJsonValue(value))
        }
        return renderedValueList
    } else if (valueToJson instanceof Batches) {
        return g.render(valueToJson)
    } else {
        return valueToJson
    }
}

if (object instanceof Map) {
    json {
        object.each { key ,value ->
            "$key" getJsonValue(value)
        }
    }
} else if (object instanceof List) {
    json getJsonValue(object)
} else {
    json g.render(object)
}

URLMappings (optional):
post "/command/$action(.$format)?"(controller: 'command')
When I am calling the post request with accept json I got null, but when I call it with application/xml the response is proper:

$ curl -d {"name":"test"}  http://localhost:9000/command/execute -H "accept:application/json"
**null**

$ curl -d {"name":"test"}  http://localhost:9000/command/execute -H "accept:application/xml"
<?xml version="1.0" encoding="UTF-8"?><list><map><entry key="object"><entry key="result">

Check database complete

Batch execution completed successfully
</entry></entry></map></list>

[nikhilsharma8193]

@VenelinPetkov

You are missing this line in your controller:

static responseFormats = ['json']

then simply use respond result

It should work.

Also, why you replaced DomainClass with Batches ? (You will have undesirable results)

Check your grails version and JSON views version. I would recommend grails >= 3.1.8 and JSON Views >= 1.1.0.* (which supports _object.gson).

[vmptk]

@nikhilsharma8193, I have applied the suggestions... Add the response formats, change the json mapper to DomainClass. The result is still the same xml type is working , while json request still returns null. I am using grails3.2.0 RC2

[nikhilsharma8193]

@VenelinPetkov

Possibilities are:

1. You created a view file for this action, if so you need to exactly map the model in your file with your response. But in this case the _object.gson file is of no use.
2. Your Grails or JSON views version may be the cause, I suspect JSON views version.

I have used this with version 3.2.0.RC1 and JSON views version 1.1.0.RC3 it worked. Try cleaning and then running.

grails clean && grails compile && grails run-app