PebbleTemplates 自定义tag&filter&function 开发简单说明

PebbleTemplates 的扩展能力还是很强大的，开发起来也比较方便，以下是一个简单的说明，更加复杂的推荐查看官方源码学习

filter 开发

参考代码
此filter 直接返回rongfengliang

 
public class LoginFilter implements Filter {

    public LoginFilter() {

    }

    @Override

    public Object apply(Object input, Map<String, Object> args, PebbleTemplate self, EvaluationContext context, int lineNumber) throws PebbleException {

        return  "rongfengliang";

    }
 
    @Override

    public List<String> getArgumentNames() {

        return null;

    }

}

function 开发

参考代码
一个输入参数返回

 
public class MyFunction implements Function {

    private final List<String> argumentNames = new ArrayList<>();

    public MyFunction() {

        this.argumentNames.add("name");

    }

    @Override

    public Object execute(Map<String, Object> args, PebbleTemplate self, EvaluationContext context, int lineNumber) {

        String name = (String) args.get("name");

        return  name;

    }
 
    @Override

    public List<String> getArgumentNames() {

      return this.argumentNames;

    }

}

tag 开发

tag 相对比较复杂，包含了tag 解析树，tag node 处理，tag node 对应业务处理,以下是一个简单的include包装，代码部分服用了现有include 的处理

参考代码
token 处理，对应tag 名称为rongfengliang

 
public class MyTokenParser implements TokenParser {

    @Override

    public String getTag() {

        return "rongfengliang";

    }
 
    @Override

    public RenderableNode parse(Token token, Parser parser) {

        TokenStream stream = parser.getStream();

        int lineNumber = token.getLineNumber();

        // skip over the 'include' token

        stream.next();

        Expression<?> includeExpression = parser.getExpressionParser().parseExpression();

        stream.expect(Token.Type.EXECUTE_END);

        return new MyIncludeNode(lineNumber, includeExpression);

    }

}

MyIncludeNode node 处理

public class MyIncludeNode extends AbstractRenderableNode {

    private final Expression<?> includeExpression;
 
    public MyIncludeNode(int lineNumber, Expression<?> includeExpression) {

        super(lineNumber);

        this.includeExpression = includeExpression;

    }
 
    @Override

    public void render(PebbleTemplateImpl self, Writer writer, EvaluationContextImpl context)

            throws IOException {

        String templateName = (String) this.includeExpression.evaluate(self, context);

        Map<?, ?> map = Collections.emptyMap();

        if (templateName == null) {

            throw new PebbleException(

                    null,

                    "The template name in an include tag evaluated to NULL. If the template name is static, make sure to wrap it in quotes.",

                    this.getLineNumber(), self.getName());

        }

       // 此处代码复用了include 部分的，需要进行include 模版的处理

        self.includeTemplate(writer, context, templateName, map);

    }
 
    @Override

    public void accept(NodeVisitor visitor) {

        visitor.visit(this);

    }
 
    public Expression<?> getIncludeExpression() {

        return this.includeExpression;

    }
 
}

扩展开发

PebbleTemplates 提供了一个方便的扩展点，可以方便进行扩展的注册，实现AbstractExtension 就可以了

参考代码

public class MyExtension extends AbstractExtension {
 
    @Override

    public Map<String, Filter> getFilters() {

        Map<String, Filter> filters = new HashMap<>();

        filters.put("rongfengliang",new LoginFilter());

        return  filters;

    }
 
    @Override

    public List<TokenParser> getTokenParsers() {

        List<TokenParser> parsers = new ArrayList<>();

        parsers.add(new MyTokenParser());

        return parsers;

    }
 
    @Override

    public Map<String, Function> getFunctions() {

        Map<String, Function> functionMap = new HashMap<>();

        functionMap.put("rongfengliang",new MyFunction());

        return  functionMap;

    }

}

注册扩展

PebbleTemplates 提供了比较方便的扩展注册方法，很简洁

参考代码

MinioClient minioClient =

                MinioClient.builder()

                        .endpoint("http://127.0.0.1:9000")

                        .credentials("minio", "minio123")

                        .build();

DelegatingLoader delegatingLoader = new DelegatingLoader(Arrays.asList(new S3Loader(minioClient,"demoapp")));

// 初始化PebbleEngine， 并进行扩展的注册

PebbleEngine engine = new PebbleEngine.Builder().loader(delegatingLoader).extension(new MyExtension()).build();

PebbleTemplate compiledTemplate = engine.getTemplate("home.html");

Map<String, Object> context = new HashMap<>();

context.put("name", "Mitchell");

Writer writer = new StringWriter();

compiledTemplate.evaluate(writer, context);

String output = writer.toString();

System.out.println(output);

使用

参考模版

// rongfengliang tag 使用

{%  rongfengliang "100/footer.html" %}

// rongfengliang 函数使用

this is demo  {{ rongfengliang('dalongdemoapp') }}

// filter 使用

 <div> {{ "demoapp" | rongfengliang }} <div>