我是一位长期读者，但是第一次写作。
我目前正在尝试在代码库中使用AspectJ实现一个记录器。 AspectJ似乎运行良好，但我遇到了非常奇怪的Java错误。我是一个长期的C ++和.Net开发人员，他仍然适应Java的世界，所以如果这是一个愚蠢的问题，我道歉。
我的代码试图捕获异常，并将相关信息记录到文本文件中。陷阱工作正常，但我注意到，当我部署时，我没有得到任何数据。我在Java反编译器中打开了我的类文件，并注意到PrintWriter似乎正在生成错误。我从来没有见过像这样的问题，所以我希望你可以有任何见解。
package mil.uscg.c3cen.vic.aspect;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.JoinPoint;
@Aspect
public class LoggingAspect
{
private final String LOG_FILE = "aspectLog.txt";
private final File file = new File(LOG_FILE);
private LoggingAspect()
{
}
private void logException(String msg)
{
try
{
if(!file.exists())
file.createNewFile();
}
catch(IOException e)
{
}
try (FileWriter fw = new FileWriter(file);
BufferedWriter bw = new BufferedWriter(fw);
PrintWriter pw = new PrintWriter(bw))
{
pw.println(msg);
}
catch(IOException e)
{
}
}
private String getSimpleFunctionInfo(String className, String function, Object[] args)
{
StringBuilder builder = new StringBuilder();
builder.append(". Method: ");
builder.append(className);
builder.append(".");
builder.append(function);
if(args.length == 0)
{
builder.append("()");
return builder.toString();
}
builder.append("(");
for(Object o : args)
{
builder.append(o.toString());
builder.append(",");
}
// Replace the comma for the last param with a closing parenthesis
int len = builder.length();
builder.replace(len -1, len, ")");
return builder.toString();
}
// Returns a formatted exception. "Exception.ErrorMessage"
private String getSimpleExceptionInfo(String name, String msg)
{
StringBuilder builder = new StringBuilder();
builder.append("Exception caught: ");
builder.append(name);
builder.append(". Message: ");
builder.append(msg);
return builder.toString();
}
@AfterThrowing(pointcut = "execution(* mil.uscg.c3cen.*.*.*(..)) "
//+ "&& !within(mil.uscg.c3cen.vic.aspect.*) "
, throwing = "excep")
public void afterThrowing(JoinPoint jp, Throwable excep) throws Throwable
{
String ex = getSimpleExceptionInfo(excep.getClass().getSimpleName(),
excep.getMessage());
String name = getSimpleFunctionInfo(jp.getSignature().getDeclaringType().getSimpleName(),
jp.getSignature().getName(),
jp.getArgs());
StringBuilder builder = new StringBuilder();
builder.append(ex);
builder.append(name);
logException(builder.toString());
}
}
除了函数logException之外，所有内容都在类文件中看起来如此。
/* Error */
private void logException(String msg)
{
// Byte code:
// 0: aload_0
// 1: getfield 25 mil/uscg/c3cen/vic/aspect/LoggingAspect:file Ljava/io/File;
// 4: invokevirtual 32 java/io/File:exists ()Z
// 7: ifne +15 -> 22
// 10: aload_0
// 11: getfield 25 mil/uscg/c3cen/vic/aspect/LoggingAspect:file Ljava/io/File;
// 14: invokevirtual 36 java/io/File:createNewFile ()Z
// 17: pop
// 18: goto +4 -> 22
// 21: pop
// 22: aconst_null
// 23: astore_2
// 24: aconst_null
// 25: astore_3
// 26: new 39 java/io/FileWriter
// 29: dup
// 30: aload_0
// 31: getfield 25 mil/uscg/c3cen/vic/aspect/LoggingAspect:file Ljava/io/File;
// 34: invokespecial 41 java/io/FileWriter:<init> (Ljava/io/File;)V
// 37: astore 4
// 39: new 44 java/io/BufferedWriter
// 42: dup
// 43: aload 4
// 45: invokespecial 46 java/io/BufferedWriter:<init> (Ljava/io/Writer;)V
// 48: astore 5
// 50: new 49 java/io/PrintWriter
// 53: dup
// 54: aload 5
// 56: invokespecial 51 java/io/PrintWriter:<init> (Ljava/io/Writer;)V
// 59: astore 6
// 61: aload 6
// 63: aload_1
// 64: invokevirtual 52 java/io/PrintWriter:println (Ljava/lang/String;)V
// 67: aload 6
// 69: ifnull +24 -> 93
// 72: aload 6
// 74: invokevirtual 55 java/io/PrintWriter:close ()V
// 77: goto +16 -> 93
// 80: astore_2
// 81: aload 6
// 83: ifnull +8 -> 91
// 86: aload 6
// 88: invokevirtual 55 java/io/PrintWriter:close ()V
// 91: aload_2
// 92: athrow
// 93: aload 5
// 95: ifnull +43 -> 138
// 98: aload 5
// 100: invokevirtual 58 java/io/BufferedWriter:close ()V
// 103: goto +35 -> 138
// 106: astore_3
// 107: aload_2
// 108: ifnonnull +8 -> 116
// 111: aload_3
// 112: astore_2
// 113: goto +13 -> 126
// 116: aload_2
// 117: aload_3
// 118: if_acmpeq +8 -> 126
// 121: aload_2
// 122: aload_3
// 123: invokevirtual 59 java/lang/Throwable:addSuppressed (Ljava/lang/Throwable;)V
// 126: aload 5
// 128: ifnull +8 -> 136
// 131: aload 5
// 133: invokevirtual 58 java/io/BufferedWriter:close ()V
// 136: aload_2
// 137: athrow
// 138: aload 4
// 140: ifnull +66 -> 206
// 143: aload 4
// 145: invokevirtual 65 java/io/FileWriter:close ()V
// 148: goto +58 -> 206
// 151: astore_3
// 152: aload_2
// 153: ifnonnull +8 -> 161
// 156: aload_3
// 157: astore_2
// 158: goto +13 -> 171
// 161: aload_2
// 162: aload_3
// 163: if_acmpeq +8 -> 171
// 166: aload_2
// 167: aload_3
// 168: invokevirtual 59 java/lang/Throwable:addSuppressed (Ljava/lang/Throwable;)V
// 171: aload 4
// 173: ifnull +8 -> 181
// 176: aload 4
// 178: invokevirtual 65 java/io/FileWriter:close ()V
// 181: aload_2
// 182: athrow
// 183: astore_3
// 184: aload_2
// 185: ifnonnull +8 -> 193
// 188: aload_3
// 189: astore_2
// 190: goto +13 -> 203
// 193: aload_2
// 194: aload_3
// 195: if_acmpeq +8 -> 203
// 198: aload_2
// 199: aload_3
// 200: invokevirtual 59 java/lang/Throwable:addSuppressed (Ljava/lang/Throwable;)V
// 203: aload_2
// 204: athrow
// 205: pop
// 206: return
// Line number table:
// Java source line #28 -> byte code offset #0
// Java source line #29 -> byte code offset #10
// Java source line #30 -> byte code offset #18
// Java source line #31 -> byte code offset #21
// Java source line #36 -> byte code offset #22
// Java source line #36 -> byte code offset #26
// Java source line #37 -> byte code offset #39
// Java source line #38 -> byte code offset #50
// Java source line #40 -> byte code offset #61
// Java source line #41 -> byte code offset #67
// Java source line #42 -> byte code offset #205
// Java source line #46 -> byte code offset #206
// Local variable table:
// start length slot name signature
// 0 207 0 this LoggingAspect
// 0 207 1 msg String
// 23 1 2 localObject1 Object
// 80 28 2 localObject2 Object
// 112 92 2 localObject3 Object
// 25 1 3 localObject4 Object
// 106 17 3 localThrowable1 Throwable
// 151 17 3 localThrowable2 Throwable
// 183 17 3 localThrowable3 Throwable
// 37 140 4 fw java.io.FileWriter
// 48 84 5 bw java.io.BufferedWriter
// 59 28 6 pw java.io.PrintWriter
// 21 1 12 localIOException1 java.io.IOException
// 205 1 13 localIOException2 java.io.IOException
// Exception table:
// from to target type
// 0 18 21 java/io/IOException
// 61 67 80 finally
// 50 93 106 finally
// 39 138 151 finally
// 26 183 183 finally
// 22 205 205 java/io/IOException
}
这真的让我很难过，所以任何信息都会非常感激。谢谢！
答案 0 :(得分：1)
好的，我尝试使用Java 8和当前的AspectJ 1.8.8。您的方面按预期工作（我编译它没有任何更改）。它有点过于复杂，应该简化。此外，您可能只是错误地计算了切入点中.*的数量。
如果我在您的建议方法的开头添加System.out.println(jp);，以便在控制台上看到某些内容并针对此示例驱动程序类运行您的方面......
package mil.uscg.c3cen.foo;
public class Application {
public static void main(String[] args) {
for (int i = 0; i < 3; i++) {
try {
doSomething();
}
catch (Exception e) {}
}
}
public static void doSomething() {
System.out.println("Calculation result = " + multiply(add(3, 4), 5));
System.out.println("Calculation result = " + divide(add(5, 6), 0));
}
private static int add(int summand1, int summand2) {
return summand1 + summand2;
}
private static int multiply(int factor1, int factor2) {
return factor1 * factor2;
}
private static int divide(int dividend, int divisor) {
return dividend / divisor;
}
}
......控制台日志如下所示：
Calculation result = 35
execution(int mil.uscg.c3cen.foo.Application.divide(int, int))
execution(void mil.uscg.c3cen.foo.Application.doSomething())
Calculation result = 35
execution(int mil.uscg.c3cen.foo.Application.divide(int, int))
execution(void mil.uscg.c3cen.foo.Application.doSomething())
Calculation result = 35
execution(int mil.uscg.c3cen.foo.Application.divide(int, int))
execution(void mil.uscg.c3cen.foo.Application.doSomething())
正如您所看到的，只记录了在调用层次结构中抛出异常的方法（直到它们被捕获），如预期的那样。日志文件 aspectLog.txt 具有以下内容：
Exception caught: ArithmeticException. Message: / by zero. Method: Application.main([Ljava.lang.String;@f6f4d33)
需要改进的地方：
mil.uscg.c3cen的所有子包。 “该包及其所有子包中的所有方法执行”的语法为execution(* mil.uscg.c3cen..*(..))。println致电后。改进＆amp;简化方面：
package mil.uscg.c3cen.vic.aspect;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintWriter;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Aspect;
@Aspect
public class LoggingAspect {
private static final String LOG_FILE = "aspectLog.txt";
private final PrintWriter logWriter;
public LoggingAspect() throws FileNotFoundException {
logWriter = new PrintWriter(new FileOutputStream(LOG_FILE));
Runtime.getRuntime().addShutdownHook(new Thread() {
@Override
public void run() {
logWriter.close();
}
});
}
@AfterThrowing(
pointcut =
"(execution(* mil.uscg.c3cen..*(..)) || execution(mil.uscg.c3cen..new(..)))" +
" && !within(mil.uscg.c3cen.vic.aspect..*) ",
throwing = "excep"
)
public void afterThrowing(JoinPoint jp, Throwable excep) throws Throwable {
//System.out.println(excep + " -> " + jp);
logWriter.println(excep + " -> " + jp);
}
}
扩展代码示例，构造函数抛出异常：
package mil.uscg.c3cen.foo;
public class Application {
public Application() {
System.out.println(1/0);
}
public static void doSomething() {
System.out.println("Calculation result = " + multiply(add(3, 4), 5));
System.out.println("Calculation result = " + divide(add(5, 6), 0));
}
private static int add(int summand1, int summand2) {
return summand1 + summand2;
}
private static int multiply(int factor1, int factor2) {
return factor1 * factor2;
}
private static int divide(int dividend, int divisor) {
return dividend / divisor;
}
public static void main(String[] args) {
for (int i = 0; i < 3; i++) {
try {
doSomething();
}
catch (Exception e) {}
}
try {
new Application();
}
catch (Exception e) {}
}
}
控制台日志：
Calculation result = 35
Calculation result = 35
Calculation result = 35
日志文件：
java.lang.ArithmeticException: / by zero -> execution(int mil.uscg.c3cen.foo.Application.divide(int, int))
java.lang.ArithmeticException: / by zero -> execution(void mil.uscg.c3cen.foo.Application.doSomething())
java.lang.ArithmeticException: / by zero -> execution(int mil.uscg.c3cen.foo.Application.divide(int, int))
java.lang.ArithmeticException: / by zero -> execution(void mil.uscg.c3cen.foo.Application.doSomething())
java.lang.ArithmeticException: / by zero -> execution(int mil.uscg.c3cen.foo.Application.divide(int, int))
java.lang.ArithmeticException: / by zero -> execution(void mil.uscg.c3cen.foo.Application.doSomething())
java.lang.ArithmeticException: / by zero -> execution(mil.uscg.c3cen.foo.Application())
查看最后一行，在构造函数中看到异常。
如果你想美化异常日志记录输出，类似于原始方面的做法，请执行以下操作：
logWriter.println(excep.getClass().getSimpleName() + " -> " + jp.getSignature());
然后日志文件变为：
ArithmeticException -> int mil.uscg.c3cen.foo.Application.divide(int, int)
ArithmeticException -> void mil.uscg.c3cen.foo.Application.doSomething()
ArithmeticException -> int mil.uscg.c3cen.foo.Application.divide(int, int)
ArithmeticException -> void mil.uscg.c3cen.foo.Application.doSomething()
ArithmeticException -> int mil.uscg.c3cen.foo.Application.divide(int, int)
ArithmeticException -> void mil.uscg.c3cen.foo.Application.doSomething()
ArithmeticException -> mil.uscg.c3cen.foo.Application()
答案 1 :(得分：0)
嗯，你并没有真正说出问题所在。如果你在logException中遇到未捕获异常的问题，那么就抓住它并进行调查。打开文件时很可能是它的权限问题，或者（例如在Windows上）操作系统不允许多个线程访问该文件。
对于第二个问题 - 字节码退出清除。第一部分非常简单，并遵循您编写的代码。第二部分处理关闭资源并将可能捕获的异常作为已抑制的异常添加到已经引发的异常。它有点长但是在相反方向上再次跟随资源初始化。