自定义java注解（二） 实现DBHelper中的getCon( )得到数据库连接

1. 定义一个DBinfo 注解

@Documented@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.METHOD)@Inheritedpublic @interface DBinfo {    public String URL() ;    public String Username() ;    public String Password() ;    public String Driver() ;}

1. 新建DBHelper，实现 getCon方法 注意导包

public class DBHelper {    @DBinfo(URL="jdbc:mysql://localhost:3306/test",Username="root",Password="Rindy_RR",Driver="com.mysql.jdbc.Driver")    public Connection getCon(String URL,String Username,String Password,String Driver){        Connection con=null;        try{            Class.forName(Driver).newInstance();            con=DriverManager.getConnection(URL,Username,Password);        } catch (Exception e) {            throw new RuntimeException(e);        }        //直接在控制台输出，看con是否成功得到        System.out.println(con.toString());        return con;    }}

1. 解析框架的实现

public class ParseDBinfo {    public void parseMethod(Class clazz) throws InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchMethodException, SecurityException{        Object obj = clazz.newInstance();        Method[] methods=clazz.getDeclaredMethods();        for(Method m:methods){            DBinfo dbinfo=m.getAnnotation(DBinfo.class);            if(dbinfo!=null){                String URL=dbinfo.URL();                String Username=dbinfo.Username();                String Password=dbinfo.Password();                String Driver=dbinfo.Driver();                //容错处理                if(URL!=null && Username!=null && Password!=null && Driver!=null && !URL.equals("") && !Username.equals("") && !Password.equals("") && !Driver.equals("")){                    m.invoke(obj, URL,Username,Password,Driver);                }else{                    System.out.println("参数不能为空！");                }            }        } }}

1. 测试类

public void testApp() throws InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchMethodException, SecurityException {        ParseDBinfo pb=new ParseDBinfo();        pb.parseMethod(DBHelper.class);    }

测试结果：

注意getCon( ) 的参数不要写错了，根据自己实际的mysql配置来，其实多写几次，还是很好理解的。下一次，自定义个Junit，@Test @Before @After