groovy 中的 get 与 getProperty

Question

让我吃惊！

根据groovy的文档，groovy可以使用"getProperty"方法获取对象的属性。因此，当我想更改在特殊对象上获取属性的行为时，我使用类别 class 来覆盖 "getProperty" 方法。但是，它不起作用。最后，我发现 groovy 框架使用类别 class 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 groovy 就是那样工作。

这是类别 class。

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);
    }

}

"get" 被调用，而不是 "getProperty"

而且，在实际情况下DynaBeanExtension是用groovy编译的。 bean的构造是用java编译的。然后通过使用 binding，我将它放入测试代码中，这是一个由 java 代码执行的运行时脚本。

Answer 1

这发生在编译本身。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
    }
}

为Groovy classes

class Foo {
    String str
}

如果你反编译 Main class，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);
    }
}

A .[property] = 调用被编译为 ScriptBytecodeAdapter.setGroovyObjectProperty，后者又调用链 MetaClassImpl.setProperty > MetaMethod.doMethodInvoke > CachedMethod.invoke > java.lang.reflect.Method.invoke > [setter]

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

为Javaclasses

如果你使用 Java 版本的 class 被调用，就像这样

public class Foo {
    private String str;

    public String getStr() {
        return str;
    }

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

同样的Main反编译为

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.setProperty(str, null, foo, (String)"str");

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

A .[property] = 调用被编译为 ScriptBytecodeAdapter.setProperty，后者又调用链 [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 arrayOfCallSite[1].callGroovyObjectGetProperty，后者又调用链 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那样，您已经正确地覆盖了 getter（因为它发生在 class 本身），但是如果您想覆盖 getProperty或 setProperty，您必须在 metaClass 中执行此操作，而不是 class 本身。您看到的行为是预期的。此代码演示如何重写每个

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

产出

in setter
in getter
in setProperty
in getProperty

并且由于 getProperty/setProperty 调用（最终）向 getter/setter 进行调度，您可以完全阻止 getter/setter 被调用，例如这个

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
}

产出

in setProperty
in getProperty

groovy 中的 get 与 getProperty

get vs getProperty in groovy

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