We define an abstract class clock, expect to be able to achieve a certain time to report time.
/**
* Clock time
*/
public abstract class Clock {
/**
* Status check
*/
abstract void checkState();
// Date formatting
private final java.text.SimpleDateFormat clockDateFormat
= new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
/**
* Format the date object as a string
*
* @param date Date object
* @return Date formatted output
*/
final String formatDate(java.util.Date date) {
return clockDateFormat.format(date);
}
/**
* Get the current time
*
* @return current time
*/
final java.util.Date nowDate() {
return new java.util.Date();
}
/**
* report time
*
* @return report time
*/
final String report() {
checkState();
return formatDate(nowDate());
}
/**
* Delay a certain time
*
* @throws InterruptedException Interrupted
*/
abstract void delay() throws InterruptedException;
/**
* Cycle time
*/
final void loopReport() throws InterruptedException {
while (true) {
try {
System.out.println(report());
} catch (Throwable cause) {
cause.printStackTrace();
}
delay();
}
}
}This clock has two implementation classes，
-
One is normal to achieve
/** * One is normal to achieve */ static class NormalClock extends Clock { @Override void checkState() { return; } @Override void delay() throws InterruptedException { Thread.sleep(1000L); } }
Run up to once every second
2017-02-27 14:48:58 2017-02-27 14:48:59 2017-02-27 14:49:00 2017-02-27 14:49:01 2017-02-27 14:49:02
- One is the damaged bell to achieve
```java
/**
* A damaged bell is realized
*/
static class BrokenClock extends Clock {
@Override
void checkState() {
throw new IllegalStateException();
}
@Override
void delay() throws InterruptedException {
Thread.sleep(10000L);
}
}
Run every 10 seconds after the time when the error will be reported
java.lang.IllegalStateException
at Clock$BrokenClock.checkState(Clock.java:77)
at Clock.report(Clock.java:40)
at Clock.loopReport(Clock.java:50)
at Clock.main(Clock.java:94)
java.lang.IllegalStateException
at Clock$BrokenClock.checkState(Clock.java:77)
at Clock.report(Clock.java:40)
at Clock.loopReport(Clock.java:50)
at Clock.main(Clock.java:94)
java.lang.IllegalStateException
at Clock$BrokenClock.checkState(Clock.java:77)
at Clock.report(Clock.java:40)
at Clock.loopReport(Clock.java:50)
at Clock.main(Clock.java:94)
java.lang.IllegalStateException
at Clock$BrokenClock.checkState(Clock.java:77)
at Clock.report(Clock.java:40)
at Clock.loopReport(Clock.java:50)
at Clock.main(Clock.java:94)
Obviously, the normal working clock is what we want to achieve, but now we are running on hand is just a damaged clock. Next, we fix this damaged clock to describe how to build a sandbox module to repair the damaged clock and explain how the module is working.
The problem lies in two parts of BrokenClock 's
- The
checkState ()method throws an exception in the implementation of the method Delay ()method in the delay of 10 seconds, it seems that when writing code accidentally knocked a 0
-
Assuming the use of MAVEN, add the sandbox module to rely on the two libraries
<!-- The sandbox module API --> <dependency> <groupId>com.alibaba.jvm.sandbox</groupId> <artifactId>sandbox-api</artifactId> <version>1.0.3</version> <scope>provided</scope> </dependency> <!-- javax.servlet package --> <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency>
/**
* Repair damaged module
*/
@Information(id = "broken-clock-tinker")
public class BrokenClockTinkerModule implements Module {
@Resource
private ModuleEventWatcher moduleEventWatcher;
@Http("/repairCheckState")
public void repairCheckState() {
moduleEventWatcher.watch(
// Match to Clock$BrokenClock#checkState ()
new NameRegexFilter("Clock\\$BrokenClock", "checkState"),
// Listen to the THROWS event and change the original method to throw an exception for normal return
new EventListener() {
@Override
public void onEvent(Event event) throws Throwable {
// 立即返回
ProcessControlException.throwReturnImmediately(null);
}
},
// Specifies that the monitored event is an exception thrown
Event.Type.THROWS
);
}
}-
Create
META-INF/service/com.alibaba.jvm.sandbox.api.Modulefile -
Paste the previous module into the contents of the file
com.github.ompc.demo.jvm.sandbox.clocktinker.BrokenClockTinkerModule
-
It is recommended to rely on all the two packages and tripartite package into a JAR file, you need to increase the configuration in the
pom.xml<build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-assembly-plugin</artifactId> <executions> <execution> <goals> <goal>attached</goal> </goals> <phase>package</phase> <configuration> <descriptorRefs> <descriptorRef>jar-with-dependencies</descriptorRef> </descriptorRefs> </configuration> </execution> </executions> </plugin> </plugins> </build>
-
Run the command to complete the package
mvn clean package -
Copy the prepared package to the user module directory
cp target/clock-tinker-1.0-SNAPSHOT-jar-with-dependencies.jar ~/.sandbox-module/ -
Start sandbox
./sandbox.sh -p 64229 -l module-mgr ACTIVE LOADED 0 0 0.0.0.1 luanjia@taobao.com
info ACTIVE LOADED 0 0 0.0.0.1 luanjia@taobao.com broken-clock-tinker ACTIVE LOADED 0 0 UNKNOW_VERSION UNKNOW_AUTHOR ```
You can see that the `broken-clock-tinker` module has been loaded correctly by the sandbox
-
Activate the fix checkState () method
./sandbox.sh -p 64229 -d 'broken-clock-tinker/repairCheckState'After a while, you will find the original has been throwing unusual clock has begun to refresh the time
java.lang.IllegalStateException at Clock$BrokenClock.checkState(Clock.java:89) at Clock.report(Clock.java:40) at Clock.loopReport(Clock.java:57) at Clock.main(Clock.java:111) java.lang.IllegalStateException at Clock$BrokenClock.checkState(Clock.java:89) at Clock.report(Clock.java:40) at Clock.loopReport(Clock.java:57) at Clock.main(Clock.java:111) 2017-02-27 21:34:44 2017-02-27 21:34:54 2017-02-27 21:35:04 2017-02-27 21:35:14 2017-02-27 21:35:24 2017-02-27 21:35:34 2017-02-27 21:35:44 2017-02-27 21:35:54 2017-02-27 21:36:04 2017-02-27 21:36:14
In the delay () method implementation of the BrokenClock class, the error is delayed by 10 seconds. It is necessary to return immediately before the method body is executed, thus preventing the execution of the method body from delaying by 10 seconds.
@Http("/repairDelay")
public void repairDelay() {
moduleEventWatcher.watch(
// Match to Clock$BrokenClock#checkState()
new NameRegexFilter("Clock\\$BrokenClock", "delay"),
// Listen to the THROWS event and change the original method to throw an exception for normal return
new EventListener() {
@Override
public void onEvent(Event event) throws Throwable {
// Delay here for 1s
Thread.sleep(1000L);
// And then immediately return, because the BEFORE event is listening, so then return immediately, the method body will not be executed
ProcessControlException.throwReturnImmediately(null);
}
},
// Specifies that the monitored event is before the method is executed
Event.Type.BEFORE
);
}Continue to pack, deploy, and after this replacement module, we perform module hot deployment replacement
./sandbox.sh -p 64229 -f
module flush finished, total=3;
Module refresh when the first will freeze the original module, and clean up the original plug the code to delete. So after the module refresh is complete, we see the previously repaired checkState () method has attacked.
2017-02-27 21:45:54
2017-02-27 21:46:04
2017-02-27 21:46:14
2017-02-27 21:46:24
2017-02-27 21:46:34
java.lang.IllegalStateException
at Clock$BrokenClock.checkState(Clock.java:89)
at Clock.report(Clock.java:40)
at Clock.loopReport(Clock.java:57)
at Clock.main(Clock.java:111)
java.lang.IllegalStateException
at Clock$BrokenClock.checkState(Clock.java:89)
at Clock.report(Clock.java:40)
at Clock.loopReport(Clock.java:57)
at Clock.main(Clock.java:111)
It does not matter, we continue to complete the repair work
-
Execute the repair command
# Fix the checkState () method ./sandbox.sh -p 64229 -d 'broken-clock-tinker/repairCheckState' # Fix the delay () method ./sandbox.sh -p 64229 -d 'broken-clock-tinker/repairDelay' -
Final problem fix
java.lang.IllegalStateException at Clock$BrokenClock.checkState(Clock.java:89) at Clock.report(Clock.java:40) at Clock.loopReport(Clock.java:57) at Clock.main(Clock.java:111) java.lang.IllegalStateException at Clock$BrokenClock.checkState(Clock.java:89) at Clock.report(Clock.java:40) at Clock.loopReport(Clock.java:57) at Clock.main(Clock.java:111) java.lang.IllegalStateException at Clock$BrokenClock.checkState(Clock.java:89) at Clock.report(Clock.java:40) at Clock.loopReport(Clock.java:57) at Clock.main(Clock.java:111) 2017-02-27 21:51:24 2017-02-27 21:51:34 2017-02-27 21:51:35 2017-02-27 21:51:36 2017-02-27 21:51:37 2017-02-27 21:51:38 2017-02-27 21:51:39
In this tutorial, we show you how to use the sandbox module to change the execution of the original method, which involves the core of the sandbox ModuleEventWatcher, the implementation of this class can be injected through the @ Resource comment.
-
Through the process of changing the
BEFOREevent, you can circumvent the execution of the original method body, thus bypassing the embarrassing thing of the delay of thedelay ()method. -
By changing the process in the
THROWSevent session, thecheckState ()method should be thrown to throw the return value.
You can even spy on, tamper with parameters, return value, throw the exception, etc., which will be able to achieve through the sandbox module. Sandbox module can help you achieve a lot of interesting features, look forward to your imagination.