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BAEL-634 javassist (#1349) 

* BEEL-634 javassist dependency

* BEEL-634 code for javassist article

* BEEL-634 test refinement

* BEEL-634 increment lib to newest version

* add test that uses reflection to verify

* add field

* add bytecode to different class
This commit is contained in:
Tomasz Lelek 2017-03-15 10:51:33 +01:00 committed by pedja4
parent 61660f5d37
commit 5cd552a16b
4 changed files with 162 additions and 1 deletions
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8
libraries/pom.xml
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@ -23,7 +23,7 @@
</plugins>
</build>
<dependencies>
<dependencies>
<!-- https://mvnrepository.com/artifact/cglib/cglib -->
<dependency>
<groupId>cglib</groupId>
@ -51,6 +51,11 @@
<artifactId>javatuples</artifactId>
<version>${javatuples.version}</version>
</dependency>
<dependency>
<groupId>org.javassist</groupId>
<artifactId>javassist</artifactId>
<version>${javaassist.version}</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.assertj/assertj-core -->
<dependency>
<groupId>org.assertj</groupId>
@ -65,6 +70,7 @@
<junit.version>4.12</junit.version>
<jasypt.version>1.9.2</jasypt.version>
<javatuples.version>1.2</javatuples.version>
<javaassist.version>3.21.0-GA</javaassist.version>
<assertj.version>3.6.2</assertj.version>
</properties>

17
libraries/src/main/java/com/baeldung/javasisst/Point.java Normal file
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@ -0,0 +1,17 @@
package com.baeldung.javasisst;
public class Point {
public int x = 0;
public int y = 0;
public Point(int x, int y) {
this.x = x;
this.y = y;
}
public void move(int x, int y) {
this.x = x;
this.y = y;
}
}

19
libraries/src/main/java/com/baeldung/javasisst/ThreeDimensionalPoint.java Normal file
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@ -0,0 +1,19 @@
package com.baeldung.javasisst;
public class ThreeDimensionalPoint {
public int x = 0;
public int y = 0;
public int z = 0;
public ThreeDimensionalPoint(int x, int y, int z) {
this.x = x;
this.y = y;
this.z = z;
}
public void move(int x, int y) {
this.x = x;
this.y = y;
}
}

119
libraries/src/test/java/com/baeldung/javassist/JavasisstTest.java Normal file
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@ -0,0 +1,119 @@
package com.baeldung.javassist;
import javassist.CannotCompileException;
import javassist.ClassPool;
import javassist.NotFoundException;
import javassist.bytecode.*;
import org.junit.Test;
import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.lang.reflect.Field;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
public class JavasisstTest {
@Test
public void givenJavasisstAPI_whenConstructClass_thenGenerateAClassFile() throws CannotCompileException, IOException, ClassNotFoundException, IllegalAccessException, InstantiationException {
//given
String classNameWithPackage = "com.baeldung.JavassistGeneratedClass";
ClassFile cf = new ClassFile(false, classNameWithPackage, null);
cf.setInterfaces(new String[]{"java.lang.Cloneable"});
FieldInfo f = new FieldInfo(cf.getConstPool(), "id", "I");
f.setAccessFlags(AccessFlag.PUBLIC);
cf.addField(f);
//when
String className = "JavassistGeneratedClass.class";
cf.write(new DataOutputStream(new FileOutputStream(className)));
//then
ClassPool classPool = ClassPool.getDefault();
Field[] fields = classPool.makeClass(cf).toClass().getFields();
assertEquals(fields[0].getName(), "id");
String classContent = new String(Files.readAllBytes(Paths.get(className)));
assertTrue(classContent.contains("java/lang/Cloneable"));
}
@Test
public void givenJavaClass_whenLoadAtByJavassist_thenTraversWholeClass() throws NotFoundException, CannotCompileException, BadBytecode {
//given
ClassPool cp = ClassPool.getDefault();
ClassFile cf = cp.get("com.baeldung.javasisst.Point").getClassFile();
MethodInfo minfo = cf.getMethod("move");
CodeAttribute ca = minfo.getCodeAttribute();
CodeIterator ci = ca.iterator();
//when
List<String> operations = new LinkedList<>();
while (ci.hasNext()) {
int index = ci.next();
int op = ci.byteAt(index);
operations.add(Mnemonic.OPCODE[op]);
}
//then
assertEquals(operations,
Arrays.asList("aload_0", "iload_1", "putfield", "aload_0", "iload_2", "putfield", "return"));
}
@Test
public void givenTableOfInstructions_whenAddNewInstruction_thenShouldConstructProperSequence() throws NotFoundException, BadBytecode, CannotCompileException, IllegalAccessException, InstantiationException {
//given
ClassFile cf = ClassPool.getDefault().get("com.baeldung.javasisst.ThreeDimensionalPoint").getClassFile();
//when
FieldInfo f = new FieldInfo(cf.getConstPool(), "id", "I");
f.setAccessFlags(AccessFlag.PUBLIC);
cf.addField(f);
ClassPool classPool = ClassPool.getDefault();
Field[] fields = classPool.makeClass(cf).toClass().getFields();
List<String> fieldsList = Stream.of(fields).map(Field::getName).collect(Collectors.toList());
assertTrue(fieldsList.contains("id"));
}
@Test
public void givenLoadedClass_whenAddConstructorToClass_shouldCreateClassWithConstructor() throws NotFoundException, CannotCompileException, BadBytecode {
//given
ClassFile cf = ClassPool.getDefault().get("com.baeldung.javasisst.Point").getClassFile();
Bytecode code = new Bytecode(cf.getConstPool());
code.addAload(0);
code.addInvokespecial("java/lang/Object", MethodInfo.nameInit, "()V");
code.addReturn(null);
//when
MethodInfo minfo = new MethodInfo(cf.getConstPool(), MethodInfo.nameInit, "()V");
minfo.setCodeAttribute(code.toCodeAttribute());
cf.addMethod(minfo);
//then
CodeIterator ci = code.toCodeAttribute().iterator();
List<String> operations = new LinkedList<>();
while (ci.hasNext()) {
int index = ci.next();
int op = ci.byteAt(index);
operations.add(Mnemonic.OPCODE[op]);
}
assertEquals(operations,
Arrays.asList("aload_0", "invokespecial", "return"));
}
}