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Enforce limit on classes loaded by Spel compiled expression loader

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Until this change a single classloader was used to load
all compiled SpEL expressions. This meant in a context where an
expression was repeatedly flipping between compiled and interpreted
mode (which can happen if in MIXED mode compilation and changing
the context around the evaluation) the classloader would continually
load a new compiled version but not orphan the old compiled version.
This eventually uses up all the memory as the number of classes
is ever increasing.

With this change classloaders are used to load 100 compiled
expressions. The 101st will be loaded by a new one. Orphaning the
old classloader means if an expression is ever recompiled there
is more likely to be no anchored references left to the older
compiled form and it can be GC'd. In the MIXED situation above it
should help alleviate the problem of older classes never being
candidates for GC.

Issue: SPR-15460
This commit is contained in:
Andy Clement
2017-04-27 11:21:27 -07:00
parent cd95f34666
commit c1edb3b5bd
2 changed files with 51 additions and 7 deletions
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21
spring-expression/src/test/java/org/springframework/expression/spel/SpelCompilationCoverageTests.java
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@@ -22,8 +22,10 @@ import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.StringTokenizer;
import org.junit.Test;
@@ -325,6 +327,25 @@ public class SpelCompilationCoverageTests extends AbstractExpressionTests {
assertEquals(3.4d, expression.getValue());
}
@Test
public void repeatedCompilation() throws Exception {
// Verifying that after a number of compilations, the classloaders
// used to load the compiled expressions are discarded/replaced.
// See SpelCompiler.loadClass()
Field f = SpelExpression.class.getDeclaredField("compiledAst");
Set<Object> classloadersUsed = new HashSet<>();
for (int i=0;i<1500;i++) { // 1500 is greater than SpelCompiler.CLASSES_DEFINED_LIMIT
expression = parser.parseExpression("4 + 5");
assertEquals(9, (int)expression.getValue(Integer.class));
assertCanCompile(expression);
f.setAccessible(true);
CompiledExpression cEx = (CompiledExpression)f.get(expression);
classloadersUsed.add(cEx.getClass().getClassLoader());
assertEquals(9, (int)expression.getValue(Integer.class));
}
assertTrue(classloadersUsed.size() > 1);
}
@SuppressWarnings("rawtypes")
@Test