groovy 中的 get 与 getProperty

Question

令我惊讶的是！

根据groovy的文档，groovy可以使用“getProperty”方法来获取对象的属性。因此，当我想更改获取特殊对象属性的行为时，我使用类别类来重写“getProperty”方法。然而，它不起作用。最后，我发现groovy框架使用类别类中的“get”方法来获取属性，即使对象不是地图。我的问题是，这是一个错误还是像这样工作。

这是类别类。

class DynaBeanExtension {

    public static void setProperty(DynaBean bean, String propertyName, def newValue) {
        try {
            PropertyUtilsBean pu = null;
            if (bean instanceof CustomWrapDynaBean) {
                pu = bean.propertyUtilsBean;
            }
            if (pu != null) {
                pu.setProperty(bean, propertyName, newValue);
            } else {
                PropertyUtils.setProperty(bean, propertyName, newValue);
            }
        } catch (IllegalArgumentException ex) {
            bean.propertyMissing(propertyName, newValue);
        }
    }

    public static def getProperty(DynaBean bean, String propertyName) {
        try {
            PropertyUtilsBean pu = null;
            if (bean instanceof CustomWrapDynaBean) {
                pu = bean.propertyUtilsBean;
            }
            if (pu != null) {
                return pu.getProperty(bean, propertyName);
            } else {
                return PropertyUtils.getProperty(bean, propertyName);
            }
        } catch (IllegalArgumentException ex) {
            return bean.propertyMissing(propertyName);
        }
    }

    public static def get(DynaBean bean, String propertyName) {
        try {
            PropertyUtilsBean pu = null;
            if (bean instanceof CustomWrapDynaBean) {
                pu = bean.propertyUtilsBean;
            }
            if (pu != null) {
                return pu.getProperty(bean, propertyName);
            } else {
                return PropertyUtils.getProperty(bean, propertyName);
            }
        } catch (IllegalArgumentException ex) {
            return bean.propertyMissing(propertyName);
        }
    }

这是测试代码：

public static class TestSubClass {

    private final int e = 3, f = 4;
    private final Map<String, Object> m = new HashMap<>();

    public int getE() {
        return e;
    }

    public int getF() {
        return f;
    }

    public Map<String, Object> getM() {
        return m;
    }

    @Override
    public String toString() {
        return "TestSubClass{" + "e=" + e + ", f=" + f + ", m=" + m + '}';
    }

}

public static class TestClass {

    private final int a = 1;
    private final TestSubClass b = new TestSubClass();

    public int getA() {
        return a;
    }

    public TestSubClass getB() {
        return b;
    }

    @Override
    public String toString() {
        return "TestClass{" + "a=" + a + ", b=" + b + '}';
    }

}

Map<String, String> pMap = new HashMap<>();
pMap.put("b.e", "c");
PropertyUtilsBean pu = new PropertyUtilsBean();
pu.setResolver(new ExResolver(pMap));
TestClass testObj = new TestClass();
DynaBean bean = new CustomWrapDynaBean(testObj, pu);

int c = use(DynaBeanExtension) {
    bean.c;
}

这是ExResolver的代码：

public class ExResolver implements Resolver {

    private static final char NESTED = '.';
    private static final char MAPPED_START = '(';
    private static final char MAPPED_END = ')';
    private static final char INDEXED_START = '[';
    private static final char INDEXED_END = ']';

    private final Resolver resolver;
    private final Map<String, String> pMap;

    public ExResolver(Map<String, String> pMap) {
        this(new DefaultResolver(), pMap);
    }

    public ExResolver(Resolver resolver, Map<String, String> pMap) {
        this.resolver = resolver;
        this.pMap = new HashMap<>(pMap);
    }

    private String resolveExpr(String expression) {
        for (Map.Entry<String, String> entry : pMap.entrySet()) {
            if (expression.startsWith(entry.getValue())) {
                String to = entry.getValue();
                if (expression.length() == entry.getValue().length()) {
                    return entry.getKey();
                } else {
                    int toTest = expression.codePointAt(to.length());
                    if (toTest == NESTED || toTest == MAPPED_START || toTest == INDEXED_START) {
                        return entry.getKey() + expression.substring(to.length(), expression.length());
                    } else {
                        return expression;
                    }
                }
            }
        }
        return expression;
    }

    @Override
    public int getIndex(String expression) {
        expression = resolveExpr(expression);
        return resolver.getIndex(expression);
    }

    @Override
    public String getKey(String expression) {
        expression = resolveExpr(expression);
        return resolver.getKey(expression);
    }

    @Override
    public String getProperty(String expression) {
        expression = resolveExpr(expression);
        return resolver.getProperty(expression);
    }

    @Override
    public boolean hasNested(String expression) {
        expression = resolveExpr(expression);
        return resolver.hasNested(expression);
    }

    @Override
    public boolean isIndexed(String expression) {
        expression = resolveExpr(expression);
        return resolver.isIndexed(expression);
    }

    @Override
    public boolean isMapped(String expression) {
        expression = resolveExpr(expression);
        return resolver.isMapped(expression);
    }

    @Override
    public String next(String expression) {
        expression = resolveExpr(expression);
        return resolver.next(expression);
    }

    @Override
    public String remove(String expression) {
        expression = resolveExpr(expression);
        return resolver.remove(expression);
    }

}

调用“get”，而不是“getProperty”

更何况，在真实情况下DynaBeanExtension是用groovy编译的。bean的构建是用java编译的。然后通过使用binding，我将其放入测试代码中，该代码是由java代码执行的运行时脚本。

Answer 1

这发生在编译本身中。让我们看一个更简单的例子。

class Main {
    static void main(def args) {
        Foo foo = new Foo()
        foo.str = ""
        foo.str
    }
}

对于 Groovy 类

class Foo {
    String str
}

如果你反编译这个Main类，你会看到它是

public class Main implements GroovyObject {
    public Main() {
        Main this;
        CallSite[] arrayOfCallSite = $getCallSiteArray();
        MetaClass localMetaClass = $getStaticMetaClass();
        this.metaClass = localMetaClass;
    }

    public static void main(String... args) {
        CallSite[] arrayOfCallSite = $getCallSiteArray();
        Foo foo = (Foo)ScriptBytecodeAdapter.castToType(arrayOfCallSite[0].callConstructor(Foo.class), Foo.class);
        String str = "";
        ScriptBytecodeAdapter.setGroovyObjectProperty(str, Main.class, foo, (String)"str");

        arrayOfCallSite[1].callGroovyObjectGetProperty(foo);
    }
}

调用.[property] =被编译为 a ScriptBytecodeAdapter.setGroovyObjectProperty，进而调用链MetaClassImpl.setProperty> MetaMethod.doMethodInvoke> CachedMethod.invoke> java.lang.reflect.Method.invoke>[setter]

并且.[property]调用被编译为 a arrayOfCallSite[1].callGroovyObjectGetProperty，进而调用链 AbstractCallSite.callGroovyObjectGetProperty> GetEffectivePogoPropertySite.getProperty> MethodMetaProperty$GetBeanMethodMetaProperty.getProperty> MetaMethod.doMethodInvoke> CachedMethod.invoke> java.lang.reflect.Method.invoke>[getter]

对于 Java 类

如果您使用被调用类的 Java 版本，如下所示

public class Main implements GroovyObject {
    public Main() {
        Main this;
        CallSite[] arrayOfCallSite = $getCallSiteArray();
        MetaClass localMetaClass = $getStaticMetaClass();
        this.metaClass = localMetaClass;
    }

    public static void main(String... args) {
        CallSite[] arrayOfCallSite = $getCallSiteArray();
        Foo foo = (Foo)ScriptBytecodeAdapter.castToType(arrayOfCallSite[0].callConstructor(Foo.class), Foo.class);
        String str = "";
        ScriptBytecodeAdapter.setGroovyObjectProperty(str, Main.class, foo, (String)"str");

        arrayOfCallSite[1].callGroovyObjectGetProperty(foo);
    }
}

同样Main反编译为

public class Foo {
    private String str;

    public String getStr() {
        return str;
    }

    public void setStr(String str) {
        this.str = str;
    }
}

调用.[property] =被编译为 a ScriptBytecodeAdapter.setProperty，依次调用链[Class].setProperty> InvokerHelper.setProperty-> MetaClassImpl.setProperty> MetaMethod.doMethodInvoke> CachedMethod.invoke> java.lang.reflect.Method.invoke>[setter]

并且.[property]调用被编译为 a arrayOfCallSite[1].callGroovyObjectGetProperty，进而调用链 AbstractCallSite.callGetProperty> GetEffectivePojoPropertySite.getProperty> MethodMetaProperty$GetBeanMethodMetaProperty.getProperty> MetaMethod.doMethodInvoke> CachedMethod.invoke> java.lang.reflect.Method.invoke>[getter]

更正您的代码

正如您从这些调度链中看到的，您已经正确地覆盖了 getter（因为它发生在类本身中），但是如果您想覆盖getPropertyor setProperty，则必须在 中执行此操作metaClass，而不是在类本身中执行此操作。您所看到的行为是预期的。此代码演示了如何重写每个

class Foo {
    String bar
}

// override using setter in category
@Category(Foo)
class FooCategory {
    public String getBar() {
        println "in getter"
    }
    public void setBar(String bar) {
        println "in setter"
    }
}
use (FooCategory) {
    Foo foo = new Foo()
    foo.bar = ""
    foo.bar
}

// override using metaClass
Foo.metaClass.getProperty { String pname ->
    println "in getProperty"
}
Foo.metaClass.setProperty { String pname, Object pValue ->
    println "in setProperty"
}
Foo foo = new Foo()
foo.bar = ""
foo.bar

输出

in setter
in getter
in setProperty
in getProperty

因为getProperty/setProperty调用（最终）将调度发送给 getter/setter，所以您可以完全阻止调用 getter/setter，如下所示

class Foo {
    String bar
}

Foo.metaClass.getProperty { String pname ->
    println "in getProperty"
}
Foo.metaClass.setProperty { String pname, Object pValue ->
    println "in setProperty"
}

@Category(Foo)
class FooCategory {
    String getBar() {
        println "in getter"
    }
    void setBar(String bar) {
        println "in setter"
    }
}

use (FooCategory) {
    Foo foo = new Foo()
    foo.bar = "hi foo1"
    foo.bar
}

输出

in setProperty
in getProperty