в 17:43, 31 мая 2010

2010-05-31T17:43:48Z

Admin: 1 версия

2010-05-31T14:39:35Z

1 версия

Новая страница

== Field: Class<?> getType() ==



<source lang="java">

import java.lang.reflect.Field;
public class Main {
public static void initIntFields(final Object obj) {
try {
Field[] fields = obj.getClass().getDeclaredFields();
for (int idx = 0; idx < fields.length; idx++) {
if (fields[idx].getType() == int.class) {
fields[idx].setAccessible(true);
fields[idx].setInt(obj, 0);
}
}
} catch (final IllegalAccessException ex) {
throw new RuntimeException(ex);
}
}
public static final void main(final String[] args) {
Integer value = new Integer("123");
System.out.println("Before: " + value);
initIntFields(value);
System.out.println("After: " + value);
}
}

</source>



== Field: getAnnotation(Class<DataField> annotationClass) ==



<source lang="java">

import java.lang.annotation.Annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Field;
public class Main {
public static void main(String[] args) {
Class d = DataBean.class;
Field fs[] = d.getFields();
for (Field f : fs) {
System.out.println(f);
Annotation a = f.getAnnotation(DataField.class);
if (a != null) {
System.out.println(f.getName());
}
}
}
}
class DataBean {
@DataField
public String name;
@DataField
public String data;
public String description;
}
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface DataField {
}

</source>



== Field: getDouble(Object obj) ==



<source lang="java">

import java.lang.reflect.Field;
public class Main {
public static void main(String[] args) throws Exception {
Object clazz = new TestClass();
String lookingForValue = "firstValue";
Field field = clazz.getClass().getField(lookingForValue);
Class clazzType = field.getType();
if (clazzType.toString().equals("double"))
System.out.println(field.getDouble(clazz));
else if (clazzType.toString().equals("int"))
System.out.println(field.getInt(clazz));

//System.out.println(field.get(clazz));
}
}
class TestClass {
public double firstValue = 3.14;
}

</source>



== Field: getGenericType() ==



<source lang="java">

/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import java.lang.reflect.Field;
import java.util.List;
public class Main<T> {
public boolean[][] b = { { false, false }, { true, true } };
public String name = "Alice";
public List<Integer> list;
public T val;
public static void main(String... args) {
try {
Class<?> c = Class.forName("FieldSpy");
Field f = c.getField("name");
System.out.format("Type: %s%n", f.getType());
System.out.format("GenericType: %s%n", f.getGenericType());
// production code should handle these exceptions more gracefully
} catch (ClassNotFoundException x) {
x.printStackTrace();
} catch (NoSuchFieldException x) {
x.printStackTrace();
}
}
}

</source>



== Field: getInt(Object obj) ==



<source lang="java">

import java.lang.reflect.Field;
public class Main {
public static void main(String[] args) throws Exception {
Object clazz = new TestClass();
String lookingForValue = "firstValue";
Field field = clazz.getClass().getField(lookingForValue);
Class clazzType = field.getType();
if (clazzType.toString().equals("double"))
System.out.println(field.getDouble(clazz));
else if (clazzType.toString().equals("int"))
System.out.println(field.getInt(clazz));

//System.out.println(field.get(clazz));
}
}
class TestClass {
public double firstValue = 3.14;
}

</source>



== Field: getModifiers() ==



<source lang="java">

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
public class Main {
public static void main(String[] args) {
String name = "java.util.Date";
try {
Class cl = Class.forName(name);
System.out.println("class " + name);
System.out.println("Its methods:");
printFields(cl);
System.out.println();
} catch (ClassNotFoundException e) {
System.out.println("Class not found.");
}
}
public static void printFields(Class cl) {
Field[] fields = cl.getDeclaredFields();
for (int i = 0; i < fields.length; i++) {
Field f = fields[i];
Class type = f.getType();
String name = f.getName();
System.out.print(Modifier.toString(f.getModifiers()));
System.out.println(" " + type.getName() + " " + name + ";");
}
}
}

</source>



== Field: get(Object obj) ==



<source lang="java">

import java.lang.reflect.Field;
import java.util.Date;
public class Main {
public static void main(String[] args) throws Exception {
Bean demo = new Bean();
Class clazz = demo.getClass();
Field field = clazz.getField("id");
field.set(demo, new Long(10));
Object value = field.get(demo);
System.out.println("Value = " + value);
field = clazz.getField("now");
field.set(null, new Date());
value = field.get(null);
System.out.println("Value = " + value);
}
}
class Bean {
public static Date now;
public Long id;
public String name;
}

</source>



== Field: isEnumConstant() ==



<source lang="java">

/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import static java.lang.System.out;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
enum Spy {
BLACK, WHITE
}
public class Main {
volatile int share;
int instance;
class Inner {
}
public static void main(String... args) {
try {
Class<?> c = Class.forName(args[0]);
int searchMods = 0x0;
for (int i = 1; i < args.length; i++) {
searchMods |= modifierFromString(args[i]);
}
Field[] flds = c.getDeclaredFields();
out.format("Fields in Class "%s" containing modifiers: %s%n", c
.getName(), Modifier.toString(searchMods));
boolean found = false;
for (Field f : flds) {
int foundMods = f.getModifiers();
// Require all of the requested modifiers to be present
if ((foundMods & searchMods) == searchMods) {
out.format("%-8s [ synthetic=%-5b enum_constant=%-5b ]%n", f
.getName(), f.isSynthetic(), f.isEnumConstant());
found = true;
}
}
if (!found) {
out.format("No matching fields%n");
}
// production code should handle this exception more gracefully
} catch (ClassNotFoundException x) {
x.printStackTrace();
}
}
private static int modifierFromString(String s) {
int m = 0x0;
if ("public".equals(s))
m |= Modifier.PUBLIC;
else if ("protected".equals(s))
m |= Modifier.PROTECTED;
else if ("private".equals(s))
m |= Modifier.PRIVATE;
else if ("static".equals(s))
m |= Modifier.STATIC;
else if ("final".equals(s))
m |= Modifier.FINAL;
else if ("transient".equals(s))
m |= Modifier.TRANSIENT;
else if ("volatile".equals(s))
m |= Modifier.VOLATILE;
return m;
}
}

</source>



== Field: isSynthetic() ==



<source lang="java">

/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import static java.lang.System.out;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
enum Spy {
BLACK, WHITE
}
public class Main {
volatile int share;
int instance;
class Inner {
}
public static void main(String... args) {
try {
Class<?> c = Class.forName(args[0]);
int searchMods = 0x0;
for (int i = 1; i < args.length; i++) {
searchMods |= modifierFromString(args[i]);
}
Field[] flds = c.getDeclaredFields();
out.format("Fields in Class "%s" containing modifiers: %s%n", c
.getName(), Modifier.toString(searchMods));
boolean found = false;
for (Field f : flds) {
int foundMods = f.getModifiers();
// Require all of the requested modifiers to be present
if ((foundMods & searchMods) == searchMods) {
out.format("%-8s [ synthetic=%-5b enum_constant=%-5b ]%n", f
.getName(), f.isSynthetic(), f.isEnumConstant());
found = true;
}
}
if (!found) {
out.format("No matching fields%n");
}
// production code should handle this exception more gracefully
} catch (ClassNotFoundException x) {
x.printStackTrace();
}
}
private static int modifierFromString(String s) {
int m = 0x0;
if ("public".equals(s))
m |= Modifier.PUBLIC;
else if ("protected".equals(s))
m |= Modifier.PROTECTED;
else if ("private".equals(s))
m |= Modifier.PRIVATE;
else if ("static".equals(s))
m |= Modifier.STATIC;
else if ("final".equals(s))
m |= Modifier.FINAL;
else if ("transient".equals(s))
m |= Modifier.TRANSIENT;
else if ("volatile".equals(s))
m |= Modifier.VOLATILE;
return m;
}
}

</source>



== Field: setAccessible(boolean flag) ==



<source lang="java">

/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import java.lang.reflect.Field;
public class Main {
public final boolean b = true;
public static void main(String... args) {
Main ft = new Main();
try {
Class<?> c = ft.getClass();
Field f = c.getDeclaredField("b");
f.setAccessible(true); // solution
f.setBoolean(ft, Boolean.FALSE); // IllegalAccessException
// production code should handle these exceptions more gracefully
} catch (NoSuchFieldException x) {
x.printStackTrace();
} catch (IllegalArgumentException x) {
x.printStackTrace();
} catch (IllegalAccessException x) {
x.printStackTrace();
}
}
}

</source>



== Field: setBoolean(Object obj, boolean z) ==



<source lang="java">

/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import java.lang.reflect.Field;
public class Main {
public final boolean b = true;
public static void main(String... args) {
Main ft = new Main();
try {
Class<?> c = ft.getClass();
Field f = c.getDeclaredField("b");
f.setAccessible(true); // solution
f.setBoolean(ft, Boolean.FALSE); // IllegalAccessException
// production code should handle these exceptions more gracefully
} catch (NoSuchFieldException x) {
x.printStackTrace();
} catch (IllegalArgumentException x) {
x.printStackTrace();
} catch (IllegalAccessException x) {
x.printStackTrace();
}
}
}

</source>



== Field: setInt(Object obj, int i) ==



<source lang="java">

/*
Before: [a=21.25, b=54.5, c=5665, d=2043, e=3121, f=1019]
After: [a=21.25, b=54.5, c=0, d=0, e=0, f=0]
*/
/*
*
* This software is granted under the terms of the Common Public License,
* CPL, which may be found at the following URL:
* http://www-124.ibm.ru/developerworks/oss/CPLv1.0.htm
*
* Copyright(c) 2003-2005 by the authors indicated in the @author tags.
* All Rights are Reserved by the various authors.
*
########## DO NOT EDIT ABOVE THIS LINE ########## */
import java.lang.reflect.Field;
/**
* Demonstrates how to set public field objects.
*
* @author
* @version $Revision: 1.3 $
*/
public class HiddenFieldModification {
/**
* Sets all int fields in an object to 0.
*
* @param obj The object to operate on.
*
* @throws RuntimeException If there is a reflection problem.
*/
public static void initIntFields(final Object obj) {
try {
Field[] fields = obj.getClass()
.getDeclaredFields();
for (int idx = 0; idx < fields.length; idx++) {
if (fields[idx].getType() == int.class) {
fields[idx].setAccessible(true);
fields[idx].setInt(obj, 0);
}
}
} catch (final IllegalAccessException ex) {
throw new RuntimeException(ex);
}
}
/**
* Demo Method.
*
* @param args Command line arguments.
*/
public static final void main(final String[] args) {
SomeNumbers value = new SomeNumbers();
System.out.println("Before: " + value);
initIntFields(value);
System.out.println("After: " + value);
}
}
class SomeNumbers {
/** A demo double. */
public double a = 21.25d;
/** A demo float. */
public float b = 54.5f;
/** A Demo int */
public int c = 5665;
/** Another demo int. */
public int d = 2043;
/** Another demo int. */
protected int e = 3121;
/** Another demo int. */
private int f = 1019;
/**
* @see java.lang.Object#toString()
*/
public String toString() {
return new String("[a=" + a + ", b=" + b + ", c=" + c + ", d=" + d + ", e=" + e
+ ", f=" + f + "]");
}
}

</source>

← Предыдущая	Версия 17:43, 31 мая 2010
(нет различий)

Java by API/java.lang.reflect/Field - История изменений

в 17:43, 31 мая 2010

Admin: 1 версия