昨天看了看注解,于是简单模拟一下hibernate

整个包:

先来看注解Table.java,主要是把实体类和表名联系起来

package annotation;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;//自定义的Annotation@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)public @interface Table {    String name() default "";}

 

然后是实体类Model.java,用刚写好的注解@Table配置一下

package annotation;//实体类@Table(name = "_model")    //用annotation配置public class Model {    private int id;    private String name;    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}

 

SessionFactory主要是读取注解配置(通过反射很easy),然后把实体类放入容器中

package annotation;import java.io.File;import java.util.HashMap;import java.util.Map;//annotation配置文件的解读public class SessionFactory {    private Map
     
       tableMap = new HashMap
      
       ();    private static SessionFactory sf = new SessionFactory();    private SessionFactory() {    }    public static SessionFactory config() throws Exception {        // 读取包名为annotation下所有class        File f = new File(System.getProperty("user.dir") + "/bin/annotation");        File[] files = f.listFiles();        for (int i = 0; i < files.length; i++) {            String fileName = files[i].getName();            // 载入class            Class clazz = Class.forName("annotation."                    + fileName.substring(0, fileName.indexOf(".")));            // 检查该类是否加有Table注解            Table t = (Table) clazz.getAnnotation(Table.class);            // 加入Table注解的放入容器中            if (t != null) {                sf.getTableMap().put(clazz, t.name());            }        }        return sf;    }    public Session openSession() {        return new Session(tableMap);    }    public Map
       
         getTableMap() {        return tableMap;    }    public void setTableMap(Map
        
          tableMap) {        this.tableMap = tableMap;    }}
        
       
      
     

 

session类主要负责数据库连接和sql语句处理

package annotation;import java.lang.reflect.Field;import java.lang.reflect.Method;import java.sql.Connection;import java.sql.DriverManager;import java.util.HashMap;import java.util.Map;//负责数据库连接,包括生成及执行sql语句public class Session {    private Map
     
       tableMap = new HashMap
      
       ();    public Session(Map
       
         tableMap) {        try {            Class.forName("com.mysql.jdbc.Driver");        } catch (ClassNotFoundException e) {            e.printStackTrace();        }        this.tableMap = tableMap;    }    // 储存    public void save(Object o) throws Exception {        Class clazz = o.getClass();        String tableName = tableMap.get(clazz);        // 表列名        String keys = "";        // 值        String vals = "";        Field[] fields = clazz.getDeclaredFields();        for (Field f : fields) {            // 构造列名            keys += f.getName() + ",";            // 得到get**方法,得到列的对应值            String ms = "get" + Character.toUpperCase(f.getName().charAt(0))                    + f.getName().substring(1);            Method m = clazz.getDeclaredMethod(ms);            Object obj = m.invoke(o, null);            if (obj instanceof Integer) {                vals += obj + ",";            }            if (obj instanceof String) {                vals += "'" + obj + "'" + ",";            }        }        keys = keys.substring(0, keys.length() - 1);        vals = vals.substring(0, vals.length() - 1);        String sql = createSaveSQL(tableName, keys, vals);        executeSQL(sql);    }    private void executeSQL(String sql) throws Exception {        Connection conn = DriverManager.getConnection(                "jdbc:mysql://localhost/test", "root", "lj123456");        conn.createStatement().execute(sql);        conn.close();    }    // 建sql语句    private String createSaveSQL(String tableName, String keys, String vals) {        String sql = "insert into " + tableName + " (" + keys + ") values ("                + vals + ")";        return sql;    }}
       
      
     

 

Main.java 来测试一下代码

package annotation;public class Main {    public static void main(String[] args) throws Exception {        SessionFactory sf = SessionFactory.config();        Session session = sf.openSession();        Model m = new Model();        m.setId(1);        m.setName("first");        session.save(m);    }}

 

结果:

 

O啦,暂时没有模拟hibernate其他注解,但原理一样,就偷偷懒呗.