JavaPoet：如何在注解中构建注解

Question

我尝试用下面的注释生成表达式：

@NamedQueries({@NamedQuery(name = "E.findAll", query = "SELECT e FROM E e")})

我尝试了下面的代码：

 .addAnnotation(AnnotationSpec.builder(NamedQueries.class)        
                .addMember( AnnotationSpec.builder(NamedQuery.class)
                    .addMember("name", "$S", "E.findAll")
                    .addMember("query", "$S", "SELECT e FROM E e)
                    .build()).build())

但由于addMember 需要字符串；这个表达式给出了错误。那么如何获得递归表达式。

是否可以在注解中构建另一个注解？

Answer 1

是的。使用 $L 并传递一个 AnmotationSpec。

ClassName beef = ClassName.get(tacosPackage, "Beef");
ClassName chicken = ClassName.get(tacosPackage, "Chicken");
ClassName option = ClassName.get(tacosPackage, "Option");
ClassName mealDeal = ClassName.get(tacosPackage, "MealDeal");
TypeSpec menu = TypeSpec.classBuilder("Menu")
    .addAnnotation(AnnotationSpec.builder(mealDeal)
        .addMember("price", "$L", 500)
        .addMember("options", "$L", AnnotationSpec.builder(option)
            .addMember("name", "$S", "taco")
            .addMember("meat", "$T.class", beef)
            .build())
        .addMember("options", "$L", AnnotationSpec.builder(option)
            .addMember("name", "$S", "quesadilla")
            .addMember("meat", "$T.class", chicken)
            .build())
        .build())
    .build();
assertThat(toString(menu)).isEqualTo(""
    + "package com.squareup.tacos;\n"
    + "\n"
    + "@MealDeal(\n"
    + "    price = 500,\n"
    + "    options = {\n"
    + "        @Option(name = \"taco\", meat = Beef.class),\n"
    + "        @Option(name = \"quesadilla\", meat = Chicken.class)\n"
    + "    }\n"
    + ")\n"
    + "class Menu {\n"
    + "}\n");

This test 是一个很好的例子来源。