Dao模式

1.加入驅(qū)動(dòng)

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驅(qū)動(dòng)包選中右鍵竹揍，add buil path呕寝，出現(xiàn)如下圖效果

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2.包結(jié)構(gòu)

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3.創(chuàng)建實(shí)體類grade

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編寫屬性达舒，alt+shift+s+o兩次只嚣，分別添加無參構(gòu)造灿渴、有參構(gòu)造洛波，alt+s+r添加set胰舆、get

4.GradeDao接口

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5.GradeDao接口的實(shí)現(xiàn)類：GradeDaoImpl，在impl包中

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6.訪問數(shù)據(jù)庫(kù)的工具類

/**
 * 訪問數(shù)據(jù)庫(kù)的工具類
 * @author Administrator
 *
 */
public class DBHelper {
    private String driver = "com.mysql.jdbc.Driver";
    private String url = "jdbc:mysql://localhost:3306/myschool?useUnicode=true&characterEncoding=UTF-8&useSSL=false&serverTimezone=UTC";
    private String username = "root";
    private String password = "123456";
    
    protected Connection conn = null;
    protected PreparedStatement pstmt = null;
    protected ResultSet rs = null;
    //獲取連接對(duì)象
    protected  Connection getConnection() {
        //1.加載驅(qū)動(dòng)
        try {
            Class.forName(driver);
            conn = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return conn;
    }
    //執(zhí)行增刪改
    protected int executeUpdate(String sql,Object... objs) {//Object... objs參數(shù)個(gè)數(shù)不限蹬挤，多個(gè)實(shí)參用逗號(hào)隔開缚窿，沒有這個(gè)參數(shù)不用寫
        int result = 0;
        try {
            getConnection();
                          pstmt = conn.prepareStatement(sql);
            //依次設(shè)置參數(shù)
            if(objs!=null) {
                for (int i = 0; i < objs.length; i++) {
                    pstmt.setObject(i+1, objs[i]);
                }
            }
            result = pstmt.executeUpdate();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            closeAll();
        }
        return result;
    }
    //執(zhí)行查詢
    protected ResultSet executeQuery(String sql,Object... objs) throws SQLException{
                getConnection();
        pstmt = conn.prepareStatement(sql);
        //依次設(shè)置參數(shù)
        if(objs!=null) {
            for (int i = 0; i < objs.length; i++) {
                pstmt.setObject(i+1, objs[i]);
            }
        }
        rs = pstmt.executeQuery();//外面調(diào)用此方法時(shí)依次取出結(jié)果集之后再釋放資源（無論是否發(fā)生異常），再調(diào)用時(shí)拋異常焰扳，所以此方法將異常拋出
        return rs;
    }
    //釋放資源
    protected void closeAll() {
        if(rs!=null) {
            try {
                rs.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(pstmt!=null) {
            try {
                pstmt.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(conn!=null) {
            try {
                conn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    } 
}

7.新增年級(jí)記錄

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8.測(cè)試新增年級(jí)

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8.增加單元測(cè)試

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8.查詢

實(shí)現(xiàn)類查詢方法

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測(cè)試類倦零，依次輸出查詢結(jié)果

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