Groovy JsonBuilder：使用变量名称的字段名称

Posted 2021-05-06

我正在使用groovy.json.JsonBuilder并且在指定字段名时遇到问题，该字段名也是当前范围中变量的名称。

这有效：

System.out.println(new GroovyShell().evaluate(
          "def builder = new groovy.json.JsonBuilder();"
        + "def age = 23;"
        + "builder.example {"
        + "  name 'Fred';"
        + "  'age1' 27;"
        + "  blah {"
        + "    foo 'bar';"
        + "  };"
        + "};"
        + "return builder.toPrettyString()"));

并产生输出：

{
    "example": {
        "name": "Fred",
        "age1": 27,
        "blah": {
            "foo": "bar"
        }
    }
}

但这失败了（由于某种原因，字段'age'与变量冲突）：

System.out.println(new GroovyShell().evaluate(
          "def builder = new groovy.json.JsonBuilder();"
        + "def age = 23;"
        + "builder.example {"
        + "  name 'Fred';"
        + "  'age' 27;"
        + "  blah {"
        + "    foo 'bar';"
        + "  };"
        + "};"
        + "return builder.toPrettyString()"));

并产生一个例外：

groovy.lang.MissingMethodException: No signature of method: java.lang.Integer.call() is applicable for argument types: (Integer) values: [27]
Possible solutions: wait(), abs(), any(), wait(long), wait(long, int), max(int, int)
    at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:72)
    at org.codehaus.groovy.runtime.callsite.PojoMetaClassSite.call(PojoMetaClassSite.java:48)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:47)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:128)
    at Script1$_run_closure1.doCall(Script1.groovy:5)
    at Script1$_run_closure1.doCall(Script1.groovy)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:104)
    at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:326)
    at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:264)
    at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1041)
    at groovy.lang.Closure.call(Closure.java:421)
    at groovy.lang.Closure.call(Closure.java:415)
    at groovy.json.JsonDelegate.cloneDelegateAndGetContent(JsonDelegate.java:91)
    at groovy.json.JsonBuilder.invokeMethod(JsonBuilder.java:314)
    at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:47)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:47)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:128)
    at Script1.run(Script1.groovy:3)
    at groovy.lang.GroovyShell.evaluate(GroovyShell.java:444)
    at groovy.lang.GroovyShell.evaluate(GroovyShell.java:482)
    at groovy.lang.GroovyShell.evaluate(GroovyShell.java:453)

我不想更改变量的名称。有没有办法强制JsonBuilder接受字段名称？正如你所看到的，我试图把它放在引号中，但这没有帮助。

答案

使用delegate.age来引用周围的闭包而不是引用变量。

System.out.println(new GroovyShell().evaluate(
          "def builder = new groovy.json.JsonBuilder();"
        + "def age = 23;"
        + "builder.example {"
        + "  name 'Fred';"
        + "  delegate.age 27;"
        + "  blah {"
        + "    foo 'bar';"
        + "  };"
        + "};"
        + "return builder.toPrettyString()"));

应该给你

{
    "example": {
        "name": "Fred",
        "age": 27,
        "blah": {
            "foo": "bar"
        }
    }
}