Polishing

Issue: SPR-14863

spring-expression/src/main/java/org/springframework/expression/spel/CodeFlow.java

@@ -28,15 +28,28 @@ import org.springframework.asm.Opcodes;
 import org.springframework.util.Assert;
 
 /**
- * Manages the class being generated by the compilation process. It records
- * intermediate compilation state as the bytecode is generated. It also includes
- * various bytecode generation helper functions.
+ * Manages the class being generated by the compilation process.
+ *
+ * <p>Records intermediate compilation state as the bytecode is generated.
+ * Also includes various bytecode generation helper functions.
  *
  * @author Andy Clement
+ * @author Juergen Hoeller
  * @since 4.1
  */
 public class CodeFlow implements Opcodes {
 
+	/**
+	 * Name of the class being generated. Typically used when generating code
+	 * that accesses freshly generated fields on the generated type.
+	 */
+	private final String className;
+
+	/**
+	 * The current class being generated.
+	 */
+	private final ClassWriter classWriter;
+
 	/**
 	 * Record the type of what is on top of the bytecode stack (i.e. the type of the
 	 * output from the previous expression component). New scopes are used to evaluate
@@ -45,17 +58,12 @@ public class CodeFlow implements Opcodes {
 	 */
 	private final Stack<ArrayList<String>> compilationScopes;
 
-	/**
-	 * The current class being generated
-	 */
-	private ClassWriter cw;
-
 	/**
 	 * As SpEL ast nodes are called to generate code for the main evaluation method
 	 * they can register to add a field to this class. Any registered FieldAdders
 	 * will be called after the main evaluation function has finished being generated.
 	 */
-	private List<FieldAdder> fieldAdders = null;
+	private List<FieldAdder> fieldAdders;
 
 	/**
 	 * As SpEL ast nodes are called to generate code for the main evaluation method
@@ -63,13 +71,7 @@ public class CodeFlow implements Opcodes {
 	 * registered ClinitAdders will be called after the main evaluation function
 	 * has finished being generated.
 	 */
-	private List<ClinitAdder> clinitAdders = null;
-
-	/**
-	 * Name of the class being generated. Typically used when generating code
-	 * that accesses freshly generated fields on the generated type.
-	 */
-	private String clazzName;
+	private List<ClinitAdder> clinitAdders;
 
 	/**
 	 * When code generation requires holding a value in a class level field, this
@@ -83,13 +85,20 @@ public class CodeFlow implements Opcodes {
 	 */
 	private int nextFreeVariableId = 1;
 
-	public CodeFlow(String clazzName, ClassWriter cw) {
-		this.compilationScopes = new Stack<>();
-		this.compilationScopes.add(new ArrayList<>());
-		this.cw = cw;
-		this.clazzName = clazzName;
+
+	/**
+	 * Construct a new {@code CodeFlow} for the given class.
+	 * @param className the name of the class
+	 * @param classWriter the corresponding ASM {@code ClassWriter}
+	 */
+	public CodeFlow(String className, ClassWriter classWriter) {
+		this.className = className;
+		this.classWriter = classWriter;
+		this.compilationScopes = new Stack<ArrayList<String>>();
+		this.compilationScopes.add(new ArrayList<String>());
 	}
 
+
 	/**
 	 * Push the byte code to load the target (i.e. what was passed as the first argument
 	 * to CompiledExpression.getValue(target, context))
@@ -103,6 +112,7 @@ public class CodeFlow implements Opcodes {
 	 * Push the bytecode to load the EvaluationContext (the second parameter passed to
 	 * the compiled expression method).
 	 * @param mv the visitor into which the load instruction should be inserted
+	 * @since 4.3.4
 	 */
 	public void loadEvaluationContext(MethodVisitor mv) {
 		mv.visitVarInsn(ALOAD, 2);
@@ -164,18 +174,18 @@ public class CodeFlow implements Opcodes {
 	public void finish() {
 		if (this.fieldAdders != null) {
 			for (FieldAdder fieldAdder : this.fieldAdders) {
-				fieldAdder.generateField(cw,this);
+				fieldAdder.generateField(this.classWriter, this);
 			}
 		}
 		if (this.clinitAdders != null) {
-			MethodVisitor mv = cw.visitMethod(ACC_PUBLIC | ACC_STATIC, "<clinit>", "()V", null, null);
+			MethodVisitor mv = this.classWriter.visitMethod(ACC_PUBLIC | ACC_STATIC, "<clinit>", "()V", null, null);
 			mv.visitCode();
-			this.nextFreeVariableId = 0; // To 0 because there is no 'this' in a clinit
+			this.nextFreeVariableId = 0;  // to 0 because there is no 'this' in a clinit
 			for (ClinitAdder clinitAdder : this.clinitAdders) {
 				clinitAdder.generateCode(mv, this);
 			}
 			mv.visitInsn(RETURN);
-			mv.visitMaxs(0,0); // not supplied due to COMPUTE_MAXS
+			mv.visitMaxs(0,0);  // not supplied due to COMPUTE_MAXS
 			mv.visitEnd();
 		}
 	}
@@ -213,13 +223,13 @@ public class CodeFlow implements Opcodes {
 	}
 
 	public String getClassName() {
-		return this.clazzName;
+		return this.className;
 	}
 
 
 	/**
 	 * Insert any necessary cast and value call to convert from a boxed type to a
-	 * primitive value
+	 * primitive value.
 	 * @param mv the method visitor into which instructions should be inserted
 	 * @param ch the primitive type desired as output
 	 * @param stackDescriptor the descriptor of the type on top of the stack