我正在尝试在 Groovy 中开发一个项目，我一直在查看我的代码并尝试找到可以用更惯用的 Groovy 替换的区域，直到找到解决方案我遇到的另一个问题 https://stackoverflow.com/questions/28355773/in-groovy-why-does-the-behaviour-of-change-for-interfaces-extending-compar.
我开始更深入地研究 AST 转换注释的使用 - 它们帮助显着减少了我在某些地方必须编写的代码量。但是，我在使用时遇到问题groovy.transform.builder.Builder使用我的不可变值类之一进行注释。该注释的来源已托管here https://github.com/groovy/groovy-core/blob/master/src/main/groovy/transform/builder/Builder.java.
问题在于，注释似乎使构建器直接设置构建者的值，而不是存储值的副本并将它们传递给构建者的构造函数。这导致ReadOnlyPropertyException当您尝试将它与不可变类一起使用时。
您可以使用此注释选择四种可能的构建器策略，其中我已经尝试过DefaultStrategy, ExternalStrategy and InitializerStrategy。然而，所有这些都引发了问题。
ExternalStrategy看起来是四个中最有前途的一个，您可以找到一个基于它的 SSCCE，详细说明了该问题here https://groovyconsole.appspot.com/script/5641206004449280.
下面还包含示例的源代码：
import groovy.transform.Immutable
import groovy.transform.builder.Builder as GBuilder
import groovy.transform.builder.ExternalStrategy
/*
* Uncommenting the below causes a failure:
* 'groovy.lang.ReadOnlyPropertyException: Cannot set readonly property: value for class: Value'
*/
//@Immutable
class Value {
@GBuilder(forClass = Value, prefix = 'set', builderStrategy = ExternalStrategy)
static class Builder { }
int value
String toString() { "Value($value)" }
}
def builder = new Value.Builder()
println builder.setValue(1).build()
似乎也有关于此事的相关 JIRA 讨论here http://jira.codehaus.org/browse/GROOVY-6484.
Edit
我尝试使用下面 CFrick 的答案，使用InitializerStrategy而不是ExternalStrategy.
现在一切都可以编译，但是当我尝试执行测试时，我在运行时收到以下错误：
java.lang.IllegalAccessError: tried to access class com.github.tagc.semver.version.BaseVersion from class com.github.tagc.semver.version.BaseVersion$com.github.tagc.semver.version.BaseVersionInitializer
at java.lang.Class.getDeclaringClass(Class.java:1227)
at java.beans.MethodRef.set(MethodRef.java:46)
at java.beans.MethodDescriptor.setMethod(MethodDescriptor.java:117)
at java.beans.MethodDescriptor.<init>(MethodDescriptor.java:72)
at java.beans.MethodDescriptor.<init>(MethodDescriptor.java:56)
at java.beans.Introspector.getTargetMethodInfo(Introspector.java:1163)
at java.beans.Introspector.getBeanInfo(Introspector.java:426)
at java.beans.Introspector.getBeanInfo(Introspector.java:173)
at com.github.tagc.semver.version.VersionFactory.createBaseVersion(VersionFactory.groovy:34)
at com.github.tagc.semver.test.util.TestSetup.<clinit>(TestSetup.groovy:77)
at java.lang.Class.forName(Class.java:344)
at com.github.tagc.semver.version.SnapshotDecoratorSpec.#decoratedVersion should be considered equal to patch-bumped #releaseVersion snapshot(SnapshotDecoratorSpec.groovy:24)
随后出现一系列异常，如下所示：
java.lang.NoClassDefFoundError: Could not initialize class com.github.tagc.semver.test.util.TestSetup
at java.lang.Class.forName(Class.java:344)
at com.github.tagc.semver.version.SnapshotDecoratorSpec.#decoratedVersion should be considered equal to minor-bumped #releaseVersion snapshot(SnapshotDecoratorSpec.groovy:36)
我现在拥有的是BaseVersion类如下：
/**
* A concrete, base implementation of {@link com.github.tagc.semver.version.Version Version}.
*
* @author davidfallah
* @since v0.1.0
*/
@Immutable
@Builder(prefix = 'set', builderStrategy = InitializerStrategy)
@PackageScope
final class BaseVersion implements Version {
// ...
/**
* The major category of this version.
*/
int major = 0
/**
* The minor category of this version.
*/
int minor = 0
/**
* The patch category of this version.
*/
int patch = 0
/**
* Whether this version is a release or snapshot version.
*/
boolean release = false
// ...
}
生产这些实例的工厂：
/**
* A factory for producing base and decorated {@code Version} objects.
*
* @author davidfallah
* @since v0.5.0
*/
class VersionFactory {
// ...
/**
* Returns an instance of {@link com.github.tagc.semver.version.BaseVersion BaseVersion} constructed
* with the given parameters.
*
* @param major the major category value of the version instance
* @param minor the minor category value of the version instance
* @param patch the patch category value of the version instance
* @param release the release setting of the version instance
* @return an instance of {@code BaseVersion}
*/
static BaseVersion createBaseVersion(int major, int minor, int patch, boolean release) {
return new BaseVersion(major, minor, patch, release)
}
/**
* Returns an instance of {@link com.github.tagc.semver.version.BaseVersion BaseVersion} constructed
* with the given parameters.
*
* @param m a map of parameter names and their corresponding values corresponding to the
* construction parameters of {@code BaseVersion}.
*
* @return an instance of {@code BaseVersion}
*/
static BaseVersion createBaseVersion(Map m) {
return new BaseVersion(m)
}
/**
* Returns an instance of {@link com.github.tagc.semver.version.BaseVersion BaseVersion} constructed
* with the given parameters.
*
* @param l a list of parameter values corresponding to the construction parameters of {@code BaseVersion}.
*
* @return an instance of {@code BaseVersion}
*/
static BaseVersion createBaseVersion(List l) {
return new BaseVersion(l)
}
/**
* Returns a builder for {@link com.github.tagc.semver.version.BaseVersion BaseVersion} to specify
* the construction parameters for the {@code BaseVersion} incrementally.
*
* @return an instance of {@code BaseVersion.Builder}
*/
static Object createBaseVersionBuilder() {
return BaseVersion.builder()
}
// ...
}
测试规范类Version对象：
/**
* Test specification for {@link com.github.tagc.semver.version.Version Version}.
*
* @author davidfallah
* @since 0.1.0
*/
@Unroll
class VersionSpec extends Specification {
static exampleVersions = [
VersionFactory.createBaseVersion(major:1, minor:2, patch:3),
VersionFactory.createBaseVersion(major:0, minor:0, patch:0),
VersionFactory.createBaseVersion(major:5, minor:4, patch:3),
VersionFactory.createBaseVersion(major:1, minor:16, patch:2),
VersionFactory.createBaseVersion(major:4, minor:5, patch:8),
]
// ...
}
以及其他尝试创建实例的类BaseVersion失败的，例如TestSetup.
