Tim On Computer Science

Many JSON formats are completely brain dead. Instead of the natural { key : value }, these formats go “all meta’, using { Field: “name”, Value: “amateur” } or { “name” : “name”, “value”: “amateur” }. This “meta key-value” approach is a stupid format that doesn’t provide any extra extensibility, yet completely destroys the concept of a useful schema.

This poor design also complicates json query (jq) (see cookbook too)

The recipe to extract the value you want:

$ jq -r '.[] | select( .Field == "properties").Value' output.json
this is a terrible design

With this input file:

$ cat output.json
[
  {
    "Field": "description",
    "Value": "human description of a terrible design"
  },
  {
    "Field": "enabled",
    "Value": true
  },
  {
    "Field": "id",
    "Value": "fa722ed8b4f56d14bcf77537"
  },
  {
    "Field": "name",
    "Value": "your-name"
  },
  {
    "Field": "properties",
    "Value": "this is a terrible design"
  }
]

GraphQL curl command examples, showing you both the curl command and the graphql schema.

Project link: graphql-java-codegen-gradle-plugin

This is documentation for the combination of:

1. A realistic graphql schema
2. An actual Java server that implements that graphql schema
3. Using curl to issue graphql commands to that server

It is amazing difficult to find all three of these together in one place.

Process:

1. clone git repository https://github.com/kobylynskyi/graphql-java-codegen-gradle-plugin
2. cd graphql-java-codegen-gradle-plugin/graphql-codegen-gradle-plugin-example
3. echo > settings.gradle
4. gradle build
5. start mongodb on port 27017 on localhost
6. gradle run
   — this starts a server on port localhost:8080

Then, in a different window, run these sample curl commands:

ADD:
Notes:
* Shows syntax for types: String, Int, BigDecimal, and enum
* Only outputs ‘size’ because that is what the query asked to get
* Shows that “mutation” is still a “query”
* Shows the correct quotation mark escaping, and where quotes are required and where they are not required

curl  \
  -X POST \
  -H "Content-Type: application/json" \
  -d '{ "query":  "mutation {  newBike(bike : { type: ROAD, brand: \"foo\", size: \"big\", year: 2000, price: 123 }) { size } }" }' \
  http://localhost:8080/graphql

Result:

{
  "data": {
    "newBike": {
      "size":"big"
    }
  }
}

FETCH:
Notes:
* shows formatting of “DateTime” field

curl  \
  -X POST \
  -H "Content-Type: application/json" \
  -d '{ "query":  "query {  bikes { id type brand size year price addedDateTime} }"  }' \
  http://localhost:8080/graphql

Result:

{
  "data": {
    "bikes": [
      {
        "id": "5e28ac4d64f0e8088f8bce47",
        "type": "ROAD",
        "brand": "foo",
        "size": "big",
        "year": 2000,
        "price": 123,
        "addedDateTime": "2020-01-22 14:10:53 -0600"
      }
    ]
  }
}

Every once in a while, at the beginning of a new project, I start the search for a command-line argument parsing library in Java. This post shows the results of examining the field as of mid 2018. This post serves both as a “which to use” and as a “which have been evaluated, and found wanting” guide.

* Best So Far
JCommander v1.71
http://jcommander.org/
annotation, good documentation, custom parser, validation

* Honorable Mention
picocli v3.3
http://picocli.info/
annotation, good documentation — documentation looks suspiciously like it is patterned after JCommander

* Pretty Good
args4j
http://args4j.kohsuke.org/
field-based, annotation-based, unclear if “–long-Name” is supported

JewelCLI
http://jewelcli.lexicalscope.com/
annotation-based, interface-based but can be instance-based with setters, has short and long names

* Also-Rans

jopt-simple
https://pholser.github.io/jopt-simple/
Key-Value – the opposite of a good library. Many of the libraries below share this same deficiency.

JArgs
http://jargs.sourceforge.net/
single “parse” call with array of options, Key-Value get value where key is the option

Jakarta Commons CLI
http://commons.apache.org/proper/commons-cli/
like JArgs, except key is “String”, not option object

argparser
http://www.cs.ubc.ca/~lloyd/java/argparser.html
create individual options, where options are “holders”, parse() into the holders

JSAP
http://www.martiansoftware.com/jsap/
old (2008), not well documented

JCommando
http://jcommando.sourceforge.net/
it generates .java, but still requires an additional .jar