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Modify SpEL code gen to take account of null safe refs

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With this change the code generation for method and property
references is modified to include branching logic in the
case of null safe dereferencing (?.). This is complicated
by the possible usage of primitives on the left hand side
of the dereference. To cope with this case primitives are
promoted to boxed types when this situation occurs enabling
null to be passed as a possible result.

Issue: SPR-16489
This commit is contained in:
Andy Clement
2018-03-12 11:11:40 -07:00
parent 573f1d77f2
commit d3acf45ea4
4 changed files with 284 additions and 15 deletions
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15
spring-expression/src/main/java/org/springframework/expression/spel/CodeFlow.java
View File

@@ -1003,4 +1003,19 @@ public class CodeFlow implements Opcodes {
void generateCode(MethodVisitor mv, CodeFlow codeflow);
}
public static String toBoxedDescriptor(String primitiveDescriptor) {
switch (primitiveDescriptor.charAt(0)) {
case 'I': return "Ljava/lang/Integer";
case 'J': return "Ljava/lang/Long";
case 'F': return "Ljava/lang/Float";
case 'D': return "Ljava/lang/Double";
case 'B': return "Ljava/lang/Byte";
case 'C': return "Ljava/lang/Character";
case 'S': return "Ljava/lang/Short";
case 'Z': return "Ljava/lang/Boolean";
default:
throw new IllegalArgumentException("Unexpected non primitive descriptor "+primitiveDescriptor);
}
}
}

46
spring-expression/src/main/java/org/springframework/expression/spel/ast/MethodReference.java
View File

@@ -24,6 +24,7 @@ import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.springframework.asm.Label;
import org.springframework.asm.MethodVisitor;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.AccessException;
@@ -53,6 +54,8 @@ public class MethodReference extends SpelNodeImpl {
private final boolean nullSafe;
private String originalPrimitiveExitTypeDescriptor = null;
private volatile CachedMethodExecutor cachedExecutor;
@@ -233,7 +236,14 @@ public class MethodReference extends SpelNodeImpl {
CachedMethodExecutor executorToCheck = this.cachedExecutor;
if (executorToCheck != null && executorToCheck.get() instanceof ReflectiveMethodExecutor) {
Method method = ((ReflectiveMethodExecutor) executorToCheck.get()).getMethod();
this.exitTypeDescriptor = CodeFlow.toDescriptor(method.getReturnType());
String descriptor = CodeFlow.toDescriptor(method.getReturnType());
if (this.nullSafe && CodeFlow.isPrimitive(descriptor)) {
originalPrimitiveExitTypeDescriptor = descriptor;
this.exitTypeDescriptor = CodeFlow.toBoxedDescriptor(descriptor);
}
else {
this.exitTypeDescriptor = descriptor;
}
}
}
@@ -293,17 +303,23 @@ public class MethodReference extends SpelNodeImpl {
boolean isStaticMethod = Modifier.isStatic(method.getModifiers());
String descriptor = cf.lastDescriptor();
if (descriptor == null) {
if (!isStaticMethod) {
// Nothing on the stack but something is needed
cf.loadTarget(mv);
}
Label skipIfNull = null;
if (descriptor == null && !isStaticMethod) {
// Nothing on the stack but something is needed
cf.loadTarget(mv);
}
else {
if (isStaticMethod) {
// Something on the stack when nothing is needed
mv.visitInsn(POP);
}
if ((descriptor != null || !isStaticMethod) && nullSafe) {
mv.visitInsn(DUP);
skipIfNull = new Label();
Label continueLabel = new Label();
mv.visitJumpInsn(IFNONNULL,continueLabel);
CodeFlow.insertCheckCast(mv, this.exitTypeDescriptor);
mv.visitJumpInsn(GOTO, skipIfNull);
mv.visitLabel(continueLabel);
}
if (descriptor != null && isStaticMethod) {
// Something on the stack when nothing is needed
mv.visitInsn(POP);
}
if (CodeFlow.isPrimitive(descriptor)) {
@@ -323,6 +339,14 @@ public class MethodReference extends SpelNodeImpl {
mv.visitMethodInsn((isStaticMethod ? INVOKESTATIC : INVOKEVIRTUAL), classDesc, method.getName(),
CodeFlow.createSignatureDescriptor(method), method.getDeclaringClass().isInterface());
cf.pushDescriptor(this.exitTypeDescriptor);
if (originalPrimitiveExitTypeDescriptor != null) {
// The output of the accessor will be a primitive but from the block above it might be null,
// so to have a 'common stack' element at skipIfNull target we need to box the primitive
CodeFlow.insertBoxIfNecessary(mv, originalPrimitiveExitTypeDescriptor);
}
if (skipIfNull != null) {
mv.visitLabel(skipIfNull);
}
}

40
spring-expression/src/main/java/org/springframework/expression/spel/ast/PropertyOrFieldReference.java
View File

@@ -21,6 +21,7 @@ import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.springframework.asm.Label;
import org.springframework.asm.MethodVisitor;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.AccessException;
@@ -47,6 +48,8 @@ public class PropertyOrFieldReference extends SpelNodeImpl {
private final boolean nullSafe;
private String originalPrimitiveExitTypeDescriptor = null;
private final String name;
private volatile PropertyAccessor cachedReadAccessor;
@@ -83,7 +86,7 @@ public class PropertyOrFieldReference extends SpelNodeImpl {
PropertyAccessor accessorToUse = this.cachedReadAccessor;
if (accessorToUse instanceof CompilablePropertyAccessor) {
CompilablePropertyAccessor accessor = (CompilablePropertyAccessor) accessorToUse;
this.exitTypeDescriptor = CodeFlow.toDescriptor(accessor.getPropertyType());
setExitTypeDescriptor(CodeFlow.toDescriptor(accessor.getPropertyType()));
}
return tv;
}
@@ -350,8 +353,40 @@ public class PropertyOrFieldReference extends SpelNodeImpl {
if (!(accessorToUse instanceof CompilablePropertyAccessor)) {
throw new IllegalStateException("Property accessor is not compilable: " + accessorToUse);
}
Label skipIfNull = null;
if (nullSafe) {
mv.visitInsn(DUP);
skipIfNull = new Label();
Label continueLabel = new Label();
mv.visitJumpInsn(IFNONNULL,continueLabel);
CodeFlow.insertCheckCast(mv, this.exitTypeDescriptor);
mv.visitJumpInsn(GOTO, skipIfNull);
mv.visitLabel(continueLabel);
}
((CompilablePropertyAccessor) accessorToUse).generateCode(this.name, mv, cf);
cf.pushDescriptor(this.exitTypeDescriptor);
if (originalPrimitiveExitTypeDescriptor != null) {
// The output of the accessor is a primitive but from the block above it might be null,
// so to have a common stack element type at skipIfNull target it is necessary
// to box the primitive
CodeFlow.insertBoxIfNecessary(mv, originalPrimitiveExitTypeDescriptor);
}
if (skipIfNull != null) {
mv.visitLabel(skipIfNull);
}
}
void setExitTypeDescriptor(String descriptor) {
// If this property or field access would return a primitive - and yet
// it is also marked null safe - then the exit type descriptor must be
// promoted to the box type to allow a null value to be passed on
if (this.nullSafe && CodeFlow.isPrimitive(descriptor)) {
this.originalPrimitiveExitTypeDescriptor = descriptor;
this.exitTypeDescriptor = CodeFlow.toBoxedDescriptor(descriptor);
}
else {
this.exitTypeDescriptor = descriptor;
}
}
@@ -379,8 +414,7 @@ public class PropertyOrFieldReference extends SpelNodeImpl {
this.ref.getValueInternal(this.contextObject, this.evalContext, this.autoGrowNullReferences);
PropertyAccessor accessorToUse = this.ref.cachedReadAccessor;
if (accessorToUse instanceof CompilablePropertyAccessor) {
this.ref.exitTypeDescriptor =
CodeFlow.toDescriptor(((CompilablePropertyAccessor) accessorToUse).getPropertyType());
this.ref.setExitTypeDescriptor(CodeFlow.toDescriptor(((CompilablePropertyAccessor) accessorToUse).getPropertyType()));
}
return value;
}