Variable not initialized in the open() method of RichMapFunction

[Yassin Marzouki]

Hi everyone,

I want to convert a stream of json strings to POJOs using Jackson, so I did the following:

.map(new RichMapFunction<String, Request>() {

    private ObjectMapper objectMapper;

        public void open() {

            objectMapper = new ObjectMapper();

        }

        @Override

             public Request map(String value) throws Exception {

                 return objectMapper.readValue(value, Request.class);

        }

})

But this code gave me a NullPointerException because the objectMapper was not initialized successfully.

1. Isn't the open() method supposed to be called before map() and initialize objectMapper?

2. I figured out that initializing objectMapper before the open() method resolves the problem, and that it works also with a simple MapFunction. In that case, is there an advantage for using a RichMapFunction?

Best,

Yassine

[Stephan Ewen]

I think you overrode the open method with the wrong signature. The right signature would be "open(Configuration cfg) {...}". You probably overlooked this because you missed the "@Override" annotation.

On Fri, Jul 22, 2016 at 4:49 PM, Yassin Marzouki <[hidden email]> wrote:

Hi everyone,

I want to convert a stream of json strings to POJOs using Jackson, so I did the following:

.map(new RichMapFunction<String, Request>() {

    private ObjectMapper objectMapper;

        public void open() {

            objectMapper = new ObjectMapper();

        }

        @Override

             public Request map(String value) throws Exception {

                 return objectMapper.readValue(value, Request.class);

        }

})

But this code gave me a NullPointerException because the objectMapper was not initialized successfully.

1. Isn't the open() method supposed to be called before map() and initialize objectMapper?

2. I figured out that initializing objectMapper before the open() method resolves the problem, and that it works also with a simple MapFunction. In that case, is there an advantage for using a RichMapFunction?

Best,

Yassine

[Dong-iL, Kim]

is open method signature right? or typo?

void open(Configuration parameters) throws Exception;

On Sat, Jul 23, 2016 at 12:09 AM, Stephan Ewen <[hidden email]> wrote:

I think you overrode the open method with the wrong signature. The right signature would be "open(Configuration cfg) {...}". You probably overlooked this because you missed the "@Override" annotation.

On Fri, Jul 22, 2016 at 4:49 PM, Yassin Marzouki <[hidden email]> wrote:

Hi everyone,

I want to convert a stream of json strings to POJOs using Jackson, so I did the following:

.map(new RichMapFunction<String, Request>() {

    private ObjectMapper objectMapper;

        public void open() {

            objectMapper = new ObjectMapper();

        }

        @Override

             public Request map(String value) throws Exception {

                 return objectMapper.readValue(value, Request.class);

        }

})

But this code gave me a NullPointerException because the objectMapper was not initialized successfully.

1. Isn't the open() method supposed to be called before map() and initialize objectMapper?

2. I figured out that initializing objectMapper before the open() method resolves the problem, and that it works also with a simple MapFunction. In that case, is there an advantage for using a RichMapFunction?

Best,

Yassine

--

[Dong-iL, Kim]

oops. stephan already answered.

sorry. T^T

On Sat, Jul 23, 2016 at 12:16 AM, Dong iL, Kim <[hidden email]> wrote:

is open method signature right? or typo?

void open(Configuration parameters) throws Exception;

On Sat, Jul 23, 2016 at 12:09 AM, Stephan Ewen <[hidden email]> wrote:

I think you overrode the open method with the wrong signature. The right signature would be "open(Configuration cfg) {...}". You probably overlooked this because you missed the "@Override" annotation.

On Fri, Jul 22, 2016 at 4:49 PM, Yassin Marzouki <[hidden email]> wrote:

Hi everyone,

I want to convert a stream of json strings to POJOs using Jackson, so I did the following:

.map(new RichMapFunction<String, Request>() {

    private ObjectMapper objectMapper;

        public void open() {

            objectMapper = new ObjectMapper();

        }

        @Override

             public Request map(String value) throws Exception {

                 return objectMapper.readValue(value, Request.class);

        }

})

But this code gave me a NullPointerException because the objectMapper was not initialized successfully.

1. Isn't the open() method supposed to be called before map() and initialize objectMapper?

2. I figured out that initializing objectMapper before the open() method resolves the problem, and that it works also with a simple MapFunction. In that case, is there an advantage for using a RichMapFunction?

Best,

Yassine

--

--

[Yassin Marzouki]

Thank you Stephan and Kim, that solved the problem.

Just to make sure, is using a MapFunction as in the following code any different? i.e. does it initialize the objectMapper for every element in the stream?

.map(new MapFunction<String, Request>() {

    private ObjectMapper objectMapper = new ObjectMapper();

        @Override

             public Request map(String value) throws Exception {

                 return objectMapper.readValue(value, Request.class);

        }

})

On Fri, Jul 22, 2016 at 5:20 PM, Dong iL, Kim <[hidden email]> wrote:

oops. stephan already answered.

sorry. T^T

On Sat, Jul 23, 2016 at 12:16 AM, Dong iL, Kim <[hidden email]> wrote:

is open method signature right? or typo?

void open(Configuration parameters) throws Exception;

On Sat, Jul 23, 2016 at 12:09 AM, Stephan Ewen <[hidden email]> wrote:

I think you overrode the open method with the wrong signature. The right signature would be "open(Configuration cfg) {...}". You probably overlooked this because you missed the "@Override" annotation.

On Fri, Jul 22, 2016 at 4:49 PM, Yassin Marzouki <[hidden email]> wrote:

Hi everyone,

I want to convert a stream of json strings to POJOs using Jackson, so I did the following:

.map(new RichMapFunction<String, Request>() {

    private ObjectMapper objectMapper;

        public void open() {

            objectMapper = new ObjectMapper();

        }

        @Override

             public Request map(String value) throws Exception {

                 return objectMapper.readValue(value, Request.class);

        }

})

But this code gave me a NullPointerException because the objectMapper was not initialized successfully.

1. Isn't the open() method supposed to be called before map() and initialize objectMapper?

2. I figured out that initializing objectMapper before the open() method resolves the problem, and that it works also with a simple MapFunction. In that case, is there an advantage for using a RichMapFunction?

Best,

Yassine

--

--

[Dong-iL, Kim]

declare objectMapper out of map class.

final ObjectMapper objectMapper = new ObjectMapper();

source.map(str -> objectMapper.readValue(value, Request.class));

On Sat, Jul 23, 2016 at 12:28 AM, Yassin Marzouki <[hidden email]> wrote:

Thank you Stephan and Kim, that solved the problem.

Just to make sure, is using a MapFunction as in the following code any different? i.e. does it initialize the objectMapper for every element in the stream?

.map(new MapFunction<String, Request>() {

    private ObjectMapper objectMapper = new ObjectMapper();

        @Override

             public Request map(String value) throws Exception {

                 return objectMapper.readValue(value, Request.class);

        }

})

On Fri, Jul 22, 2016 at 5:20 PM, Dong iL, Kim <[hidden email]> wrote:

oops. stephan already answered.

sorry. T^T

On Sat, Jul 23, 2016 at 12:16 AM, Dong iL, Kim <[hidden email]> wrote:

is open method signature right? or typo?

void open(Configuration parameters) throws Exception;

On Sat, Jul 23, 2016 at 12:09 AM, Stephan Ewen <[hidden email]> wrote:

I think you overrode the open method with the wrong signature. The right signature would be "open(Configuration cfg) {...}". You probably overlooked this because you missed the "@Override" annotation.

On Fri, Jul 22, 2016 at 4:49 PM, Yassin Marzouki <[hidden email]> wrote:

Hi everyone,

I want to convert a stream of json strings to POJOs using Jackson, so I did the following:

.map(new RichMapFunction<String, Request>() {

    private ObjectMapper objectMapper;

        public void open() {

            objectMapper = new ObjectMapper();

        }

        @Override

             public Request map(String value) throws Exception {

                 return objectMapper.readValue(value, Request.class);

        }

})

But this code gave me a NullPointerException because the objectMapper was not initialized successfully.

1. Isn't the open() method supposed to be called before map() and initialize objectMapper?

2. I figured out that initializing objectMapper before the open() method resolves the problem, and that it works also with a simple MapFunction. In that case, is there an advantage for using a RichMapFunction?

Best,

Yassine

--

--

--

[Stephan Ewen]

Initializing in "open(Configuration)" means that the ObjectMapper is created only in the cluster once the MapFunction is started.

Otherwise it is created before (on the client) and Serialization-copied into the cluster, together with the MapFunction.

If the second approach works well (i.e., the ObjectMapper is serialization friendly), then there is no downside to it.

On Fri, Jul 22, 2016 at 6:01 PM, Dong iL, Kim <[hidden email]> wrote:

declare objectMapper out of map class.

final ObjectMapper objectMapper = new ObjectMapper();

source.map(str -> objectMapper.readValue(value, Request.class));

On Sat, Jul 23, 2016 at 12:28 AM, Yassin Marzouki <[hidden email]> wrote:

Thank you Stephan and Kim, that solved the problem.

Just to make sure, is using a MapFunction as in the following code any different? i.e. does it initialize the objectMapper for every element in the stream?

.map(new MapFunction<String, Request>() {

    private ObjectMapper objectMapper = new ObjectMapper();

        @Override

             public Request map(String value) throws Exception {

                 return objectMapper.readValue(value, Request.class);

        }

})

On Fri, Jul 22, 2016 at 5:20 PM, Dong iL, Kim <[hidden email]> wrote:

oops. stephan already answered.

sorry. T^T

On Sat, Jul 23, 2016 at 12:16 AM, Dong iL, Kim <[hidden email]> wrote:

is open method signature right? or typo?

void open(Configuration parameters) throws Exception;

On Sat, Jul 23, 2016 at 12:09 AM, Stephan Ewen <[hidden email]> wrote:

I think you overrode the open method with the wrong signature. The right signature would be "open(Configuration cfg) {...}". You probably overlooked this because you missed the "@Override" annotation.

On Fri, Jul 22, 2016 at 4:49 PM, Yassin Marzouki <[hidden email]> wrote:

Hi everyone,

I want to convert a stream of json strings to POJOs using Jackson, so I did the following:

.map(new RichMapFunction<String, Request>() {

    private ObjectMapper objectMapper;

        public void open() {

            objectMapper = new ObjectMapper();

        }

        @Override

             public Request map(String value) throws Exception {

                 return objectMapper.readValue(value, Request.class);

        }

})

But this code gave me a NullPointerException because the objectMapper was not initialized successfully.

1. Isn't the open() method supposed to be called before map() and initialize objectMapper?

2. I figured out that initializing objectMapper before the open() method resolves the problem, and that it works also with a simple MapFunction. In that case, is there an advantage for using a RichMapFunction?

Best,

Yassine

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