Output files are named as the templates with the ending stripped.
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6 changed files with 30 additions and 34 deletions
35
README.md
35
README.md
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@ -4,7 +4,6 @@ This is a converter tool that reads a DSL and generates output files.
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Endgen is Open Source Software using the [Apache Software License v2.0](http://www.apache.org/licenses/LICENSE-2.0)
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## Motivation
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The motivation behind this tool is that I wanted to generate boilerplate code for handling HTTP Endpoints (hence the
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endgen name).
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@ -23,25 +22,24 @@ parser and a code generator using [freemarker](https://freemarker.apache.org).
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| Endgen |
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-------------------------------------------------
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----------- ||--------| |-----------| |------------||
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| endpoint | || Parser | | In-Memory | | Freemarker || ---------------
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| endpoint | || Parser | | In-Memory | | Freemarker || ------------------
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| file | --> || | --> | AST | --> | engine || --> | Output file |
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\__________\ ||--------| |-----------| |------------|| \_____________\
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------------------------------------------------- -
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\__________\ ||--------| |-----------| |------------|| | mytemplate.xxx |
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-------------------------------------------------- \________________\
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^
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----------------
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| Template.ftl |
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\_______________\
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----------------------
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| mytemplate.xxx.ftl |
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\____________________\
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```
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## How to Run
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You need a Java 24 runtime and java in the path. A very convenient way to install a java runtime is [SdkMan](https://sdkman.io).
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Unpack the archive, run the provided shellscript file.
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### Usage
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```
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Usage: EndpointsCLI [-hvV] [-o=<outputDir>] [-t=<templateDir>] <file>
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Usage: run.sh [-hvV] [-o=<outputDir>] [-t=<templateDir>] <file>
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Generate source code from an endpoints specification file.
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<file> The source endpoints DSL file.
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-h, --help Show this help message and exit.
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@ -55,28 +53,28 @@ Generate source code from an endpoints specification file.
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```
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## DSL example
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In the simplest form the DSL looks like this
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```
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/some/endpoint <- SomeType(foo:String)
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```
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This gets parsed into an [AST](https://en.wikipedia.org/wiki/Abstract_syntax_tree) which is this case holds a list of
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This gets parsed into an [AST](https://en.wikipedia.org/wiki/Abstract_syntax_tree) which in this case holds a list of
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Path segments and a data strucutre representing the input/body type.
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## Code generation example
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When the parser is done reading the DSL it will look in a directory for [freemarker](https://freemarker.apache.org)
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templates. For each template it finds it sends in the AST. The resulting file (per template) is written to an
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output directory.
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The templates must have the file ending `.ftl` - this ending is stripped when generating the output file. So a template
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called `types.java.ftl` will generate a file called `types.java`.
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The idea being that you can take these files and probably adapt them before checking them into your project. Endgen
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does not aim to be a roundtrip tool (i.e. reading the generated source, or being smart in updating them etc). It is also
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a very limited DSL, you can for example not express what type of HTTP Verb to use or declare response codes. There are
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no plans to extend the DSL to do that either.
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## DSL
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This is the ANTLR grammar for the root of the DSL
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```antlrv4
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@ -89,7 +87,7 @@ Here is an example:
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```
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{
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package: se.rutdev.senash,
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ending: .scala
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mykey: myvalue
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}
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/some/endpoint <- SomeType(foo:String)
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@ -98,7 +96,7 @@ Embedded(foo:Bar)
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/some/other/endpoint <- (bar:Seq[Embedded])
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```
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This consists of a config block with 2 items, the 'package' and the 'ending' deinfition. These are available to be used
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This consists of a config block with 2 items, the 'package' and the 'mykey' definition. These are available to be used
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in the freemarker template as a Map of String-keys to String-values.
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`/some/endpoint <- SomeType(foo:String)` is an endpoint declaration. It declares one endpoint that have a request body
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@ -113,7 +111,6 @@ just named field-name and the other string is named field-type.
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to a specific endpoint.
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### Automatically named data types
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`/some/other/endpoint <- (bar:Seq[Embedded])` is another endpoint declaration. However this time the request body is
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not named in the DSL. But all datatypes must have a name so it will simply name it after the last path segment and
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tack on the string 'Request' at the end. So the AST till contain a datatype named `endpointRequest` with a field named
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@ -126,7 +123,6 @@ decide to generate in the templates.
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The only 'semantic' validation the parser performs is to check that not two types have the same name.
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### Reponse data types
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It is possible to have an optional response data type declared like so:
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`/some/other/endpoint <- (bar:Seq[Embedded]) -> ResponseType(foo: Bar)`
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@ -135,12 +131,10 @@ The right pointing arrow `->` denotes a response type, it can be an anonymous da
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name it from the last path segment and add 'Response' to the end of the data type name.
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### DSL config
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The only key in the config block the generator looks at is called `ending`, this will be used as the file ending for
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the resulting file of applying the freemarker template.
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## Generating
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If the parser is successful it will hold the following data in the AST
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```java
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@ -162,14 +156,12 @@ This will be passed to the freemarker engine as the 'root' data object, meaning
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That is, you can directly reference `typeDefinitions`, `endpoints` or `config`.
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### Config
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The config object is simply a String-map with the keys and values unfiltered from the input file. Here is an example
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that writes the value for a config key called 'package'.
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`package ${config.package}`
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### Data types
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These are all the data types the parser have collected, either from explicit declarations, request payloads and response
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bodies.
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@ -191,7 +183,6 @@ object Protocol:
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```
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### Endpoints
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The parser will collect the following data for endpoint declarations
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```java
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@ -33,6 +33,8 @@ public class Generator {
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private final DocumentNode data;
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private final Path outputDir;
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private final Configuration cfg;
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private final String TEMPLATE_EXTENSION = ".ftl";
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private final int TEMPLATE_EXTENSION_LENGTH = TEMPLATE_EXTENSION.length();
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public Generator(Path templatesDir, DocumentNode data, Path outputDir) throws IOException {
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this.templatesDir = Objects.requireNonNull(templatesDir);
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@ -49,13 +51,16 @@ public class Generator {
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public List<Path> generate() throws IOException, TemplateException {
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try (Stream<Path> files = Files.list(templatesDir)) {
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List<Path> templates = files.filter(p -> p.toString().endsWith(".ftl")).toList() ;
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List<String> templates = files
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.map(Path::getFileName)
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.map(Path::toString)
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.filter(p -> p.length() > TEMPLATE_EXTENSION_LENGTH && p.endsWith(TEMPLATE_EXTENSION)
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)
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.toList();
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ArrayList<Path> out = new ArrayList<>();
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for (Path template : templates) {
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String configEnding = this.data.config().get("ending") ;
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String ending = configEnding != null ? configEnding.trim() : "";
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Path outpath = outputDir.resolve(outputFilenameFromTemplate(template.getFileName(), ending));
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Template ftl = this.cfg.getTemplate(template.getFileName().toString()) ;
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for (String template : templates) {
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Path outpath = outputDir.resolve(outputFilenameFromTemplate(template));
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Template ftl = this.cfg.getTemplate(template);
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try (var outw = Files.newBufferedWriter(outpath, StandardCharsets.UTF_8)) {
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ftl.process(this.data, outw);
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out.add(outpath);
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@ -65,7 +70,7 @@ public class Generator {
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}
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}
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private String outputFilenameFromTemplate(Path template, String ending) {
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return template.getFileName().toString().replace(".ftl", ending);
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private String outputFilenameFromTemplate(String template) {
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return template.substring(0, template.length() - TEMPLATE_EXTENSION_LENGTH);
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}
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}
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