2019-4-22 jdbc学习笔记

jdbc

一.定义：java database connector

二.常用的接口

java.sql.Driver  驱动

java.sql.Connection  链接

　　java.sql.Statement    静态处理块

　　java.sql.PreparedStatement   预处理模块

　　java.sql.ResultSet  结果集

　　java.sql.ResultSetMeteData  数据库信息数据集

三.使用方法：

　　注意：oracle和mysql的jdbc 的jar包是不一样的

　　1.导入jar包

　　2.编译jar包

url=jdbc:oracle:thin:@localhost:1521:ORCL
username=SCOTT
password=root

public class DBUtils {
    private static String url = "";
    private static String username = "";
    private static String password = "";

    static{
        try {
            //加载驱动
            Class.forName("oracle.jdbc.driver.OracleDriver");
            //通过当前的线程获取类加载器，再获取资源获取器（不然不能读取到相对路径）
            InputStream stream = Thread.currentThread()
                    .getContextClassLoader()
                    .getResourceAsStream("dao/db.properties");
            //通过properties读取流中的配置信息
            Properties properties = new Properties();
            properties.load(stream);

            url = properties.getProperty("url");
            username = properties.getProperty("username");
            password = properties.getProperty("password");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 获取链接的方法
     * @return
     */
    public static Connection getConnection(){
        Connection connect = null;
        //创建驱动对象
        Driver driver = new OracleDriver();
        try {
            //将驱动对象加入到驱动对象管理器中
            DriverManager.deregisterDriver(driver);
            //通过驱动对象管理器获取链接
            connect
                    = DriverManager
                    .getConnection(url,username,password);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connect;
    }

    /**
     * 获取sql语句传达器
     * @return
     */
    public Statement getStatement(){
        Statement st = null;
        try {
           st =  new DBUtils().getConnection().createStatement();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return st;
    }

    /**
     * 获取编译好的PrepareStatement
     * @param psql 带问号的sql语句
     * @param args 与问好相对应的参数
     * @return
     */
    public PreparedStatement getPrepareStatement(String psql,Object... args){
        PreparedStatement pst = null;
        //获取链接
        Connection conn = new DBUtils().getConnection();
        try {
            //产生预编译执行器
            pst = conn.prepareStatement(psql);
            for (int i = 0; i < args.length; i++) {
                //给预编译注入参数
                pst.setObject(i+1,args[i]);
            }
            ResultSet resultSet = pst.executeQuery();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return pst;
    }

    /**
     * 释放Connection PrepareStation ResultSet的资源
     * @param conn
     */
    public void release(AutoCloseable... conn){
        for (int i = 0; i < conn.length; i++) {
            try {
                if(conn[i]!=null){
                    conn[i].close();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    @Test
    /***
     * 测试链接是否成功的方法
     */
    public void test(){
        System.out.println(new DBUtils().getConnection());
    }
}

    /**
     * 获取表信息数据集
     * @return
     */
    public DatabaseMetaData getDatabaseMetaData(){
        try {
            return DBUtils.getConnection().getMetaData();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    public void getAllTableNames(){
        //获取链接
        Connection connection =
                DBUtils.getConnection();
        try {
            //获取表数据集
            DatabaseMetaData metaData = this.getDatabaseMetaData();
            ResultSet tables = metaData.getTables(null, null, null, new String[]{"TABLE"});
            while(tables.next()){
                //获取表名
                String tableName = tables.getString("TABLE_NAME");
                System.out.println(tableName);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    //输出列名、类型、注释
    public void printColumnInfo(DatabaseMetaData databaseMetaData)throws Exception{
        ResultSet rs = databaseMetaData.getColumns(null, "%", "EMP", "%");
        while(rs.next()){
            //列名
            String columnName = rs.getString("COLUMN_NAME");
            //类型
            String typeName = rs.getString("TYPE_NAME");
            //注释
            String remarks = rs.getString("REMARKS");
            System.out.println(columnName + "--" + typeName + "--" + remarks);
        }
    }

//测试基础查询语句
    public void testStatement(){
        Connection conn =
                new DBUtils().getConnection();
        try(Statement statement = conn.createStatement()){
            ResultSet resultSet = statement.executeQuery("SELECT * FROM EMP");
            while(resultSet.next()){
                System.out.print(resultSet.getString("ENAME")+" ");
                System.out.println(resultSet.getInt("SAL"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    /**
     * 当要大量插入数据的时候使用batch更快
     */
    public void testBatch(){
        Connection conn = DBUtils.getConnection();
        try {
            PreparedStatement ps = conn.prepareStatement("INSERT INTO EMPTEMP(NAME,AGE) VALUES(?,?)");
            for (int i = 1; i < 1000; i++) {
                ps.setString(1,"小王"+i);
                ps.setInt(2,i);
                //将当前的指令存储到batch中
                ps.addBatch();
            }
            ps.executeBatch();
            ps.close();
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }