Java字节码实现Aop(续一)

以下代码需要asm-5.0.2.jar和asm-commons-5.0.2.jar两个包。

package com.shihuan.field;

public class AccountField {

	String sql = "select * from tables";
	
	public void operation() {
        System.out.println("shihuan operation...");
    }

    int executeInternal() {
		System.out.println("shihuan executeInternal...");
		return 1;
	}
	
}

package com.shihuan.field;

public class TestAccountField {

	public static void main(String[] args) {
		AccountField t = new AccountField();
		t.operation();
        t.executeInternal();
	}

}

package com.shihuan.field;

public class SecurityCheckerField {

	public static java.util.Date getStartTime() {
		long starttime = System.currentTimeMillis();
		java.util.Date startdate = new java.util.Date(starttime);
		System.out.println("shihuan starttime --->> " + startdate);
		return startdate;
	}
	
	public static void checkCode(AccountField afObj) {
		long endtime = System.currentTimeMillis();
		java.util.Date enddate = new java.util.Date(endtime);
		System.out.println("shihuan endtime --->> " + enddate);
		System.out.println(afObj.sql);
	}
	
}

package com.shihuan.field;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

public class GeneratorAsmField {

	public static void main(String[] args) throws IOException {
		ClassReader cr = new ClassReader("com.shihuan.field.AccountField");
		ClassWriter cw = new ClassWriter(cr, ClassWriter.COMPUTE_MAXS);
		ClassVisitor cv = new ClassVisitor(Opcodes.ASM5, cw) {
			
			public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
				MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions); // 先得到原始的方法
				MethodVisitor newMethod = mv;

				if (mv != null) {
					if ("executeInternal".equals(name)) { // 此处的executeInternal即为需要修改的方法，修改方法內容
						// 访问需要修改的方法
						newMethod = new MethodVisitor(Opcodes.ASM5, mv) {

							public void visitCode() {
								visitMethodInsn(
										Opcodes.INVOKESTATIC,
										"com/shihuan/field/SecurityCheckerField",
										"getStartTime", "()Ljava/util/Date;", false);
								super.visitCode();
							}
							
							public void visitInsn(int opcode) {
								if ((opcode >= Opcodes.IRETURN && opcode <= Opcodes.RETURN) || opcode == Opcodes.ATHROW) {
									visitVarInsn(Opcodes.ALOAD, 0);
									visitMethodInsn(Opcodes.INVOKESTATIC, "com/shihuan/field/SecurityCheckerField", "checkCode", "(Lcom/shihuan/field/AccountField;)V", false);
								}
								super.visitInsn(opcode);
							}
							
						};

					}
				}
				return newMethod;
			}

		};
		cr.accept(cv, ClassReader.SKIP_DEBUG);

		byte[] code = cw.toByteArray();
		OutputStream fos = new FileOutputStream("D:/myworkspace/JavaAsm/bin/com/shihuan/field/AccountField.class");
		fos.write(code);
		fos.close();
	}

}