使用ASM操作Java字节码，实现AOP原理

来源：互联网发布：网络神豪系统txt下载编辑：程序博客网时间：2024/05/16 19:26

本文通过一个的例子来实现：使用ASM动态生成Java字节码文件（.class）或者加载字节码后动态修改字节码，添加我们需要执行的代码，来模拟实现spring AOP。

年底了，也没心情抠字了，把写demo包含的几个类代码直接贴出来吧，代码拷贝下来后可以直接使用，不会有什么其他错误。
使用 asm-5.0.3.jar
demo工程的package为com.shanhy.demo.asm.hello

5个Java文件：
AopClassAdapter.java 用来处理哪些方法需要进行修改
AopInteceptor.java 要修改的方法中，准备添加的我们自己的代码逻辑
AopMethodVisitor.java 修改字节码
HelloGeneratorClass.java 通过asm动态生成java类，测试的main方法也在这里
MyClassLoader.java 自定义ClassLoader

package com.shanhy.demo.asm.hello;import org.objectweb.asm.ClassVisitor;import org.objectweb.asm.MethodVisitor;import org.objectweb.asm.Opcodes;public class AopClassAdapter extends ClassVisitor implements Opcodes {    public AopClassAdapter(int api, ClassVisitor cv) {        super(api, cv);    }    @Override    public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {        MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions);        // 对test开头的方法进行特殊处理        if (name.startsWith("test")) {            mv = new AopMethodVisitor(this.api, mv);        }        return mv;    }}1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24

package com.shanhy.demo.asm.hello;public class AopInteceptor {    public static void before(){        System.out.println(".......before().......");    }    public static void after(){        System.out.println(".......after().......");    }}1
2
3
4
5
6
7
8
9
10
11
12
13
14
1
2
3
4
5
6
7
8
9
10
11
12
13
14

package com.shanhy.demo.asm.hello;import org.objectweb.asm.MethodVisitor;import org.objectweb.asm.Opcodes;public class AopMethodVisitor extends MethodVisitor implements Opcodes {    public AopMethodVisitor(int api, MethodVisitor mv) {        super(api, mv);    }    @Override    public void visitCode() {        super.visitCode();        this.visitMethodInsn(INVOKESTATIC, "com/shanhy/demo/asm/hello/AopInteceptor", "before", "()V", false);    }    @Override    public void visitInsn(int opcode) {        if (opcode >= IRETURN && opcode <= RETURN)// 在返回之前安插after 代码。            this.visitMethodInsn(INVOKESTATIC, "com/shanhy/demo/asm/hello/AopInteceptor", "after", "()V", false);        super.visitInsn(opcode);    }}1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

package com.shanhy.demo.asm.hello;import java.io.File;import java.io.FileOutputStream;import java.lang.reflect.Method;import org.objectweb.asm.ClassReader;import org.objectweb.asm.ClassWriter;import org.objectweb.asm.FieldVisitor;import org.objectweb.asm.Label;import org.objectweb.asm.MethodVisitor;import org.objectweb.asm.Opcodes;/** * 通过ASM生成类的字节码 *  * @author Administrator * */public class HelloGeneratorClass implements Opcodes {    /**     * 使用构造Hello类class字节码<br/>     * package中的Hello.java只是代码原型，本例中只供对比用，没有实际使用到这个类。<br/>     * ASM代码生成工具使用 bytecode     *     * @return     * @throws Exception     * @author SHANHY     * @create 2016年2月3日     */    public static byte[] generatorHelloClass() throws Exception {        ClassWriter cw = new ClassWriter(0);        FieldVisitor fv;        MethodVisitor mv;        cw.visit(V1_7, ACC_PUBLIC + ACC_SUPER, "com/shanhy/demo/asm/hello/Hello", null, "java/lang/Object", null);        cw.visitSource("Hello.java", null);        {            fv = cw.visitField(ACC_PUBLIC + ACC_FINAL + ACC_STATIC, "FLAG", "Ljava/lang/String;", null,                    "\u6211\u662f\u5e38\u91cf");            fv.visitEnd();        }        {            mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);            mv.visitCode();            Label l0 = new Label();            mv.visitLabel(l0);            mv.visitVarInsn(ALOAD, 0);            mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);            mv.visitInsn(RETURN);            Label l1 = new Label();            mv.visitLabel(l1);            mv.visitMaxs(1, 1);            mv.visitEnd();        }        {            mv = cw.visitMethod(ACC_PUBLIC, "display", "()V", null, null);            mv.visitCode();            Label l0 = new Label();            mv.visitLabel(l0);            mv.visitInsn(ICONST_0);            mv.visitVarInsn(ISTORE, 1);            Label l1 = new Label();            mv.visitLabel(l1);            Label l2 = new Label();            mv.visitJumpInsn(GOTO, l2);            Label l3 = new Label();            mv.visitLabel(l3);            mv.visitFrame(Opcodes.F_APPEND, 1, new Object[] { Opcodes.INTEGER }, 0, null);            mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");            mv.visitLdcInsn(">>>>>>>>>>\u6211\u662f\u5e38\u91cf");            mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);            Label l4 = new Label();            mv.visitLabel(l4);            mv.visitIincInsn(1, 1);            mv.visitLabel(l2);            mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);            mv.visitVarInsn(ILOAD, 1);            mv.visitIntInsn(BIPUSH, 8);            mv.visitJumpInsn(IF_ICMPLT, l3);            Label l5 = new Label();            mv.visitLabel(l5);            mv.visitInsn(RETURN);            Label l6 = new Label();            mv.visitLabel(l6);            mv.visitMaxs(2, 2);            mv.visitEnd();        }        {            mv = cw.visitMethod(ACC_PUBLIC, "testList", "()Ljava/util/List;", "()Ljava/util/List<Ljava/lang/String;>;",                    null);            mv.visitCode();            Label l0 = new Label();            mv.visitLabel(l0);            mv.visitTypeInsn(NEW, "java/util/ArrayList");            mv.visitInsn(DUP);            mv.visitMethodInsn(INVOKESPECIAL, "java/util/ArrayList", "<init>", "()V", false);            mv.visitVarInsn(ASTORE, 1);            Label l1 = new Label();            mv.visitLabel(l1);            mv.visitVarInsn(ALOAD, 1);            mv.visitLdcInsn("Tome");            mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true);            mv.visitInsn(POP);            Label l2 = new Label();            mv.visitLabel(l2);            mv.visitVarInsn(ALOAD, 1);            mv.visitLdcInsn("Jack");            mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true);            mv.visitInsn(POP);            Label l3 = new Label();            mv.visitLabel(l3);            mv.visitVarInsn(ALOAD, 1);            mv.visitLdcInsn("Lily");            mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true);            mv.visitInsn(POP);            Label l4 = new Label();            mv.visitLabel(l4);            mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");            mv.visitTypeInsn(NEW, "java/lang/StringBuilder");            mv.visitInsn(DUP);            mv.visitLdcInsn(">>>>>>>>>>testList > list.size = ");            mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "(Ljava/lang/String;)V", false);            mv.visitVarInsn(ALOAD, 1);            mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "size", "()I", true);            mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(I)Ljava/lang/StringBuilder;",                    false);            mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false);            mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);            Label l5 = new Label();            mv.visitLabel(l5);            mv.visitVarInsn(ALOAD, 1);            mv.visitInsn(ARETURN);            Label l6 = new Label();            mv.visitLabel(l6);            mv.visitMaxs(4, 2);            mv.visitEnd();        }        {            mv = cw.visitMethod(ACC_PUBLIC + ACC_VARARGS, "testMapList", "(Z[Ljava/util/Map;)Ljava/util/List;",                    "(Z[Ljava/util/Map<Ljava/lang/String;Ljava/lang/String;>;)Ljava/util/List<Ljava/util/Map<Ljava/lang/String;Ljava/lang/String;>;>;",                    null);            mv.visitCode();            Label l0 = new Label();            mv.visitLabel(l0);            mv.visitTypeInsn(NEW, "java/util/ArrayList");            mv.visitInsn(DUP);            mv.visitMethodInsn(INVOKESPECIAL, "java/util/ArrayList", "<init>", "()V", false);            mv.visitVarInsn(ASTORE, 3);            Label l1 = new Label();            mv.visitLabel(l1);            mv.visitVarInsn(ILOAD, 1);            Label l2 = new Label();            mv.visitJumpInsn(IFEQ, l2);            Label l3 = new Label();            mv.visitLabel(l3);            mv.visitVarInsn(ALOAD, 2);            mv.visitInsn(DUP);            mv.visitVarInsn(ASTORE, 7);            mv.visitInsn(ARRAYLENGTH);            mv.visitVarInsn(ISTORE, 6);            mv.visitInsn(ICONST_0);            mv.visitVarInsn(ISTORE, 5);            Label l4 = new Label();            mv.visitJumpInsn(GOTO, l4);            Label l5 = new Label();            mv.visitLabel(l5);            mv.visitFrame(Opcodes.F_FULL, 8,                    new Object[] { "com/shanhy/demo/asm/hello/Hello", Opcodes.INTEGER, "[Ljava/util/Map;",                            "java/util/List", Opcodes.TOP, Opcodes.INTEGER, Opcodes.INTEGER, "[Ljava/util/Map;" },                    0, new Object[] {});            mv.visitVarInsn(ALOAD, 7);            mv.visitVarInsn(ILOAD, 5);            mv.visitInsn(AALOAD);            mv.visitVarInsn(ASTORE, 4);            Label l6 = new Label();            mv.visitLabel(l6);            mv.visitVarInsn(ALOAD, 3);            mv.visitVarInsn(ALOAD, 4);            mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true);            mv.visitInsn(POP);            Label l7 = new Label();            mv.visitLabel(l7);            mv.visitIincInsn(5, 1);            mv.visitLabel(l4);            mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);            mv.visitVarInsn(ILOAD, 5);            mv.visitVarInsn(ILOAD, 6);            mv.visitJumpInsn(IF_ICMPLT, l5);            mv.visitLabel(l2);            mv.visitFrame(Opcodes.F_FULL, 4, new Object[] { "com/shanhy/demo/asm/hello/Hello", Opcodes.INTEGER,                    "[Ljava/util/Map;", "java/util/List" }, 0, new Object[] {});            mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");            mv.visitTypeInsn(NEW, "java/lang/StringBuilder");            mv.visitInsn(DUP);            mv.visitLdcInsn(">>>>>>>>>>testMapList > list.size = ");            mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "(Ljava/lang/String;)V", false);            mv.visitVarInsn(ALOAD, 3);            mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "size", "()I", true);            mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(I)Ljava/lang/StringBuilder;",                    false);            mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false);            mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);            Label l8 = new Label();            mv.visitLabel(l8);            mv.visitVarInsn(ALOAD, 3);            mv.visitInsn(ARETURN);            Label l9 = new Label();            mv.visitLabel(l9);            mv.visitMaxs(4, 8);            mv.visitEnd();        }        cw.visitEnd();        return cw.toByteArray();    }    /**     * 生成保存class文件     *     * @param args     * @author SHANHY     * @create 2016年2月3日     */    public static void main3(String[] args) {        try {            byte[] data = generatorHelloClass();            File file = new File("H:/Hello.class");            FileOutputStream fos = new FileOutputStream(file);            fos.write(data);            fos.close();        } catch (Exception e) {            e.printStackTrace();        }    }    /**     * AOP测试     *     * @param args     * @author SHANHY     * @create  2016年2月3日     */    public static void main(String[] args) {        try {            byte[] data = generatorHelloClass();            ClassWriter cw = new ClassWriter(0);            ClassReader cr = new ClassReader(data);            cr.accept(new AopClassAdapter(ASM5,  cw), ClassReader.SKIP_DEBUG);            data = cw.toByteArray();            MyClassLoader myClassLoader = new MyClassLoader();            Class<?> helloClass = myClassLoader.defineClass("com.shanhy.demo.asm.hello.Hello", data);            Object obj = helloClass.newInstance();            Method method = helloClass.getMethod("display", null);            method.invoke(obj, null);            method = helloClass.getMethod("testList", null);            Object result = method.invoke(obj, null);            System.out.println(result);            Class<?> stuClass = Thread.currentThread().getContextClassLoader().loadClass("com.shanhy.demo.asm.example.StudentServiceImpl");            obj = stuClass.newInstance();            method = stuClass.getMethod("print", String.class);            System.out.println(method.invoke(obj, "单单"));        } catch (Exception e) {            e.printStackTrace();        }    }}1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277

package com.shanhy.demo.asm.hello;import org.objectweb.asm.Opcodes;/** * 自定义ClassLoader * * @author   单红宇(365384722) * @myblog  http://blog.csdn.net/catoop/ * @create    2016年2月2日 */public class MyClassLoader extends ClassLoader implements Opcodes {    public MyClassLoader() {        super();    }    public MyClassLoader(ClassLoader parent) {        super(parent);    }    @Override    public Class<?> loadClass(String name) throws ClassNotFoundException {        return super.loadClass(name);    }    public Class<?> defineClass(String name, byte[] b){        return super.defineClass(name, b, 0, b.length);    }}1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32

最后这个是我们动态生成的Hello类的源码原型。

package com.shanhy.demo.asm.hello;import java.util.ArrayList;import java.util.List;import java.util.Map;public class Hello {    // 声明 一个常量    public static final String FLAG = "我是常量";    // 普通方法    public void display(){        for (int i = 0; i < 8; i++) {            System.out.println(">>>>>>>>>>" + FLAG);        }    }    // 带有List返回值    public List<String> testList(){        List<String> list = new ArrayList<>();        list.add("Tome");        list.add("Jack");        list.add("Lily");        System.out.println(">>>>>>>>>>testList > list.size = " + list.size());        return list;    }    // 泛型返回值，包含List和Map    // 两个参数，参数为Map动参    public List<Map<String, String>> testMapList(boolean val, Map<String, String>... map){        List<Map<String, String>> list = new ArrayList<>();        if(val){            for (Map<String, String> m : map) {                list.add(m);            }        }        System.out.println(">>>>>>>>>>testMapList > list.size = " + list.size());        return list;    }}1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42

仅供参考，关于ASM的API看看官方文档即可。bytecode这个Eclipse插件大家可以用一下，用了你就知道是干什么的了。
实际项目中一般不需要我们去用字节码来生成类，只有在特殊需求的时候才会使用。
话说“不常用的东西解决不常见的问题”嘛。

0 0