mirror of
https://github.com/sjsdfg/effective-java-3rd-chinese.git
synced 2025-01-17 07:40:09 +08:00
update 88. 保护性的编写 readObject 方法
This commit is contained in:
sjsdfg
parent
6ee0415b96
commit
08b83634d8
@ -5,31 +5,31 @@
|
||||
```Java
|
||||
// Immutable class that uses defensive copying
|
||||
public final class Period {
|
||||
private final Date start;
|
||||
private final Date end;
|
||||
/**
|
||||
* @param start the beginning of the period
|
||||
* @param end the end of the period; must not precede start
|
||||
* @throws IllegalArgumentException if start is after end
|
||||
* @throws NullPointerException if start or end is null
|
||||
*/
|
||||
public Period(Date start, Date end) {
|
||||
this.start = new Date(start.getTime());
|
||||
this.end = new Date(end.getTime());
|
||||
if (this.start.compareTo(this.end) > 0)
|
||||
throw new IllegalArgumentException(
|
||||
start + " after " + end);
|
||||
}
|
||||
public Date start () {
|
||||
return new Date(start.getTime());
|
||||
}
|
||||
public Date end () {
|
||||
return new Date(end.getTime());
|
||||
}
|
||||
public String toString() {
|
||||
return start + " - " + end;
|
||||
}
|
||||
... // Remainder omitted
|
||||
private final Date start;
|
||||
private final Date end;
|
||||
/**
|
||||
* @param start the beginning of the period
|
||||
* @param end the end of the period; must not precede start
|
||||
* @throws IllegalArgumentException if start is after end
|
||||
* @throws NullPointerException if start or end is null
|
||||
*/
|
||||
public Period(Date start, Date end) {
|
||||
this.start = new Date(start.getTime());
|
||||
this.end = new Date(end.getTime());
|
||||
if (this.start.compareTo(this.end) > 0)
|
||||
throw new IllegalArgumentException(
|
||||
start + " after " + end);
|
||||
}
|
||||
public Date start () {
|
||||
return new Date(start.getTime());
|
||||
}
|
||||
public Date end () {
|
||||
return new Date(end.getTime());
|
||||
}
|
||||
public String toString() {
|
||||
return start + " - " + end;
|
||||
}
|
||||
... // Remainder omitted
|
||||
}
|
||||
```
|
||||
|
||||
@ -43,36 +43,36 @@ public final class Period {
|
||||
|
||||
```Java
|
||||
public class BogusPeriod {
|
||||
// Byte stream couldn't have come from a real Period instance!
|
||||
private static final byte[] serializedForm = {
|
||||
(byte)0xac, (byte)0xed, 0x00, 0x05, 0x73, 0x72, 0x00, 0x06,
|
||||
0x50, 0x65, 0x72, 0x69, 0x6f, 0x64, 0x40, 0x7e, (byte)0xf8,
|
||||
0x2b, 0x4f, 0x46, (byte)0xc0, (byte)0xf4, 0x02, 0x00, 0x02,
|
||||
0x4c, 0x00, 0x03, 0x65, 0x6e, 0x64, 0x74, 0x00, 0x10, 0x4c,
|
||||
0x6a, 0x61, 0x76, 0x61, 0x2f, 0x75, 0x74, 0x69, 0x6c, 0x2f,
|
||||
0x44, 0x61, 0x74, 0x65, 0x3b, 0x4c, 0x00, 0x05, 0x73, 0x74,
|
||||
0x61, 0x72, 0x74, 0x71, 0x00, 0x7e, 0x00, 0x01, 0x78, 0x70,
|
||||
0x73, 0x72, 0x00, 0x0e, 0x6a, 0x61, 0x76, 0x61, 0x2e, 0x75,
|
||||
0x74, 0x69, 0x6c, 0x2e, 0x44, 0x61, 0x74, 0x65, 0x68, 0x6a,
|
||||
(byte)0x81, 0x01, 0x4b, 0x59, 0x74, 0x19, 0x03, 0x00, 0x00,
|
||||
0x78, 0x70, 0x77, 0x08, 0x00, 0x00, 0x00, 0x66, (byte)0xdf,
|
||||
0x6e, 0x1e, 0x00, 0x78, 0x73, 0x71, 0x00, 0x7e, 0x00, 0x03,
|
||||
0x77, 0x08, 0x00, 0x00, 0x00, (byte)0xd5, 0x17, 0x69, 0x22,
|
||||
0x00, 0x78
|
||||
// Byte stream couldn't have come from a real Period instance!
|
||||
private static final byte[] serializedForm = {
|
||||
(byte)0xac, (byte)0xed, 0x00, 0x05, 0x73, 0x72, 0x00, 0x06,
|
||||
0x50, 0x65, 0x72, 0x69, 0x6f, 0x64, 0x40, 0x7e, (byte)0xf8,
|
||||
0x2b, 0x4f, 0x46, (byte)0xc0, (byte)0xf4, 0x02, 0x00, 0x02,
|
||||
0x4c, 0x00, 0x03, 0x65, 0x6e, 0x64, 0x74, 0x00, 0x10, 0x4c,
|
||||
0x6a, 0x61, 0x76, 0x61, 0x2f, 0x75, 0x74, 0x69, 0x6c, 0x2f,
|
||||
0x44, 0x61, 0x74, 0x65, 0x3b, 0x4c, 0x00, 0x05, 0x73, 0x74,
|
||||
0x61, 0x72, 0x74, 0x71, 0x00, 0x7e, 0x00, 0x01, 0x78, 0x70,
|
||||
0x73, 0x72, 0x00, 0x0e, 0x6a, 0x61, 0x76, 0x61, 0x2e, 0x75,
|
||||
0x74, 0x69, 0x6c, 0x2e, 0x44, 0x61, 0x74, 0x65, 0x68, 0x6a,
|
||||
(byte)0x81, 0x01, 0x4b, 0x59, 0x74, 0x19, 0x03, 0x00, 0x00,
|
||||
0x78, 0x70, 0x77, 0x08, 0x00, 0x00, 0x00, 0x66, (byte)0xdf,
|
||||
0x6e, 0x1e, 0x00, 0x78, 0x73, 0x71, 0x00, 0x7e, 0x00, 0x03,
|
||||
0x77, 0x08, 0x00, 0x00, 0x00, (byte)0xd5, 0x17, 0x69, 0x22,
|
||||
0x00, 0x78
|
||||
};
|
||||
public static void main(String[] args) {
|
||||
Period p = (Period) deserialize(serializedForm);
|
||||
System.out.println(p);
|
||||
Period p = (Period) deserialize(serializedForm);
|
||||
System.out.println(p);
|
||||
}
|
||||
// Returns the object with the specified serialized form
|
||||
static Object deserialize(byte[] sf) {
|
||||
try {
|
||||
try {
|
||||
return new ObjectInputStream(
|
||||
new ByteArrayInputStream(sf)).readObject();
|
||||
}
|
||||
catch (IOException | ClassNotFoundException e) {
|
||||
throw new IllegalArgumentException(e);
|
||||
}
|
||||
new ByteArrayInputStream(sf)).readObject();
|
||||
}
|
||||
catch (IOException | ClassNotFoundException e) {
|
||||
throw new IllegalArgumentException(e);
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
@ -85,10 +85,10 @@ public class BogusPeriod {
|
||||
// readObject method with validity checking - insufficient!
|
||||
private void readObject(ObjectInputStream s)
|
||||
throws IOException, ClassNotFoundException {
|
||||
s.defaultReadObject();
|
||||
// Check that our invariants are satisfied
|
||||
if (start.compareTo(end) > 0)
|
||||
throw new InvalidObjectException(start +" after "+ end);
|
||||
s.defaultReadObject();
|
||||
// Check that our invariants are satisfied
|
||||
if (start.compareTo(end) > 0)
|
||||
throw new InvalidObjectException(start +" after "+ end);
|
||||
}
|
||||
```
|
||||
|
||||
@ -96,45 +96,45 @@ private void readObject(ObjectInputStream s)
|
||||
|
||||
```Java
|
||||
public class MutablePeriod {
|
||||
// A period instance
|
||||
public final Period period;
|
||||
// period's start field, to which we shouldn't have access
|
||||
public final Date start;
|
||||
// period's end field, to which we shouldn't have access
|
||||
public final Date end;
|
||||
|
||||
public MutablePeriod() {
|
||||
try {
|
||||
ByteArrayOutputStream bos =
|
||||
new ByteArrayOutputStream();
|
||||
ObjectOutputStream out =
|
||||
new ObjectOutputStream(bos);
|
||||
// Serialize a valid Period instance
|
||||
out.writeObject(new Period(new Date(), new Date()));
|
||||
/*
|
||||
// A period instance
|
||||
public final Period period;
|
||||
// period's start field, to which we shouldn't have access
|
||||
public final Date start;
|
||||
// period's end field, to which we shouldn't have access
|
||||
public final Date end;
|
||||
|
||||
public MutablePeriod() {
|
||||
try {
|
||||
ByteArrayOutputStream bos =
|
||||
new ByteArrayOutputStream();
|
||||
ObjectOutputStream out =
|
||||
new ObjectOutputStream(bos);
|
||||
// Serialize a valid Period instance
|
||||
out.writeObject(new Period(new Date(), new Date()));
|
||||
/*
|
||||
* Append rogue "previous object refs" for internal
|
||||
* Date fields in Period. For details, see "Java
|
||||
* Object Serialization Specification," Section 6.4.
|
||||
*/
|
||||
byte[] ref = { 0x71, 0, 0x7e, 0, 5 };
|
||||
// Ref #5
|
||||
bos.write(ref);
|
||||
// The start field
|
||||
ref[4] = 4;
|
||||
// Ref # 4
|
||||
bos.write(ref);
|
||||
// The end field
|
||||
// Deserialize Period and "stolen" Date references
|
||||
ObjectInputStream in = new ObjectInputStream(
|
||||
new ByteArrayInputStream(bos.toByteArray()));
|
||||
period = (Period) in.readObject();
|
||||
start = (Date) in.readObject();
|
||||
end = (Date) in.readObject();
|
||||
}
|
||||
catch (IOException | ClassNotFoundException e) {
|
||||
throw new AssertionError(e);
|
||||
}
|
||||
}
|
||||
byte[] ref = { 0x71, 0, 0x7e, 0, 5 };
|
||||
// Ref #5
|
||||
bos.write(ref);
|
||||
// The start field
|
||||
ref[4] = 4;
|
||||
// Ref # 4
|
||||
bos.write(ref);
|
||||
// The end field
|
||||
// Deserialize Period and "stolen" Date references
|
||||
ObjectInputStream in = new ObjectInputStream(
|
||||
new ByteArrayInputStream(bos.toByteArray()));
|
||||
period = (Period) in.readObject();
|
||||
start = (Date) in.readObject();
|
||||
end = (Date) in.readObject();
|
||||
}
|
||||
catch (IOException | ClassNotFoundException e) {
|
||||
throw new AssertionError(e);
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
@ -142,15 +142,15 @@ public class MutablePeriod {
|
||||
|
||||
```Java
|
||||
public static void main(String[] args) {
|
||||
MutablePeriod mp = new MutablePeriod();
|
||||
Period p = mp.period;
|
||||
Date pEnd = mp.end;
|
||||
// Let's turn back the clock
|
||||
pEnd.setYear(78);
|
||||
System.out.println(p);
|
||||
// Bring back the 60s!
|
||||
pEnd.setYear(69);
|
||||
System.out.println(p);
|
||||
MutablePeriod mp = new MutablePeriod();
|
||||
Period p = mp.period;
|
||||
Date pEnd = mp.end;
|
||||
// Let's turn back the clock
|
||||
pEnd.setYear(78);
|
||||
System.out.println(p);
|
||||
// Bring back the 60s!
|
||||
pEnd.setYear(69);
|
||||
System.out.println(p);
|
||||
}
|
||||
```
|
||||
|
||||
@ -169,13 +169,13 @@ Wed Nov 22 00:21:29 PST 2017 - Sat Nov 22 00:21:29 PST 1969
|
||||
// readObject method with defensive copying and validity checking
|
||||
private void readObject(ObjectInputStream s)
|
||||
throws IOException, ClassNotFoundException {
|
||||
s.defaultReadObject();
|
||||
// Defensively copy our mutable components
|
||||
start = new Date(start.getTime());
|
||||
end = new Date(end.getTime());
|
||||
// Check that our invariants are satisfied
|
||||
if (start.compareTo(end) > 0)
|
||||
throw new InvalidObjectException(start +" after "+ end);
|
||||
s.defaultReadObject();
|
||||
// Defensively copy our mutable components
|
||||
start = new Date(start.getTime());
|
||||
end = new Date(end.getTime());
|
||||
// Check that our invariants are satisfied
|
||||
if (start.compareTo(end) > 0)
|
||||
throw new InvalidObjectException(start +" after "+ end);
|
||||
}
|
||||
```
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user