Question

求帮忙解释这个sql的java代码

将java程序链接到MySQL的代码，能帮忙具体解释一下吗
public class DBConn {
private static final String DRIVER = "com.mysql.jdbc.Driver";
private static final String URL = "jdbc:mysql://127.0.0.1:3306/words";
private static final String USERNAME = "root";
private static final String PASSWORD = "root";
private static Connection conn;
private Statement stmt;
private ResultSet rs;
public DBConn() {
}
public static synchronized Connection getConn() {
try {
Class.forName(DRIVER);
conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
} catch (Exception e) {
e.printStackTrace();
}
return conn;
}
public void init(Connection conn) {
try {
stmt = conn.createStatement();
} catch (Exception e) {
}
}
public void close() {
try {
if (rs != null)
rs.close();
} catch (Exception e) {
}
try {
if (stmt != null)
stmt.close();
} catch (Exception e) {
}
try {
if (conn != null)
conn.close();
} catch (Exception e) {
}
}
public int select(String sql) {
int k = -10;
init(getConn());
try {
k = 0;
rs = stmt.executeQuery(sql);
if (rs.next())
k++;
} catch (Exception e) {
k = -1;
close();
}
close();
return k;
}
public int update(String sql) {
int k = -10;
init(getConn());
try {
k = 0;
k = stmt.executeUpdate(sql);
} catch (Exception e) {
k = -1;
}
close();
return k;
}
public static void main(String[] args)throws Exception {
DBConn db = new DBConn();
/**
* ��ȡ���ӵ���ݿ����
*/
System.out.println(db.getConn().getCatalog());
}
public static String getDate() {
return new SimpleDateFormat("yyyy-MM-dd hh-mm-ss").format(Calendar
.getInstance().getTime());
}
public String chStr(String str) {
String temp2;
byte temp[] = null;
try {
temp = str.getBytes("ISO8859-1");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
temp2 = new String(temp);
return temp2;
}
public ResultSet query(String sql) {
init(getConn());
try {
rs = stmt.executeQuery(sql);
} catch (Exception e) {
}
return rs;
}
}

Answer 1

public class DBConn {
private static final String DRIVER = "com.mysql.jdbc.Driver"; //定义数据库驱动
private static final String URL = "jdbc:mysql://127.0.0.1:3306/words"; //数据库所在位置，127.0.0.1代表本机，3306是数据库端口，words是数据库名
private static final String USERNAME = "root"; //用户名
private static final String PASSWORD = "root";//密码
private static Connection conn; //定义一个变量：等会用来创建数据库连接
private Statement stmt; //定义一个 statement对象，等会用来执行SQL语句用的
private ResultSet rs; //定义结果集，等会用来存放查询结果
public DBConn() {//构造方法
}
public static synchronized Connection getConn() {
try {//获取数据库连接，调用该方法即可获得一个数据库连接
Class.forName(DRIVER);
conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
} catch (Exception e) {
e.printStackTrace();
}
return conn;//返回数据库连接
}
public void init(Connection conn) {
try {//init()方法需要传入一个 conn 连接做参数，然后用这个conn连接创建statement对象，调用该方法即可拿到一个statement对象来使用。
stmt = conn.createStatement();
} catch (Exception e) {
}
}
public void close() {
try {//执行完所有操作后，调用该方法来关闭数据库连接
if (rs != null)
rs.close();
} catch (Exception e) {
}
try {
if (stmt != null)
stmt.close();
} catch (Exception e) {
}
try {
if (conn != null)
conn.close();
} catch (Exception e) {
}
}
public int select(String sql) {//输入一个 sql 字符串，即查询语句
int k = -10;
init(getConn()); //调用init()方法可以获得一个statement对象，调用getConn可以获得一个数据库连接
k = 0;
rs = stmt.executeQuery(sql); //执行查询语句，把结果放到rs结果集里
if (rs.next())//遍历RS结果集
k++;//用K来统计RS记录条数，貌似有点多余……
} catch (Exception e) {
k = -1;
close();//调用关闭数据库连接方法
}
close();
return k;
}
public int update(String sql) {//执行更新 sql 语句
int k = -10;
init(getConn());
try {
k = 0;
k = stmt.executeUpdate(sql);
} catch (Exception e) {
k = -1;
}
close();
return k;
}
public static void main(String[] args)throws Exception {
DBConn db = new DBConn();
/**
* ��ȡ���ӵ���ݿ����
*/
System.out.println(db.getConn().getCatalog());
}
public static String getDate() {
return new SimpleDateFormat("yyyy-MM-dd hh-mm-ss").format(Calendar
.getInstance().getTime());
}
public String chStr(String str) {
String temp2;
byte temp[] = null;
try {
temp = str.getBytes("ISO8859-1");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
temp2 = new String(temp);
return temp2;
}
public ResultSet query(String sql) {
init(getConn());
try {
rs = stmt.executeQuery(sql);
} catch (Exception e) {
}
return rs;
}
}

Answer 2

将java程序链接到MySQL的代码，能帮忙具体解释一下吗
public class DBConn {
//数据库连接参数
private static final String DRIVER = "com.mysql.jdbc.Driver";
private static final String URL = "jdbc:mysql://127.0.0.1:3306/words";
private static final String USERNAME = "root";
private static final String PASSWORD = "root";
private static Connection conn; //声明连接
private Statement stmt; //声明预编译
private ResultSet rs; //声明结果集
public DBConn() {
}
public static synchronized Connection getConn() {
try {
Class.forName(DRIVER); //加载数据库驱动
conn = DriverManager.getConnection(URL, USERNAME, PASSWORD); //连接数据库，其中参数为上面定义的
} catch (Exception e) {
e.printStackTrace();
}
return conn;
}
public void init(Connection conn) {
try {
stmt = conn.createStatement(); //获取预编译域
} catch (Exception e) {
}
}
public void close() { //关闭数据库方法（结果集、预编译域、数据库连接都要关闭）
try {
if (rs != null)
rs.close();
} catch (Exception e) {
}
try {
if (stmt != null)
stmt.close();
} catch (Exception e) {
}
try {
if (conn != null)
conn.close();
} catch (Exception e) {
}
}
public int select(String sql) { //查询数据库方法 （参数为sql查询语句）
int k = -10;
init(getConn()); //初始化、获取连接
try {
k = 0;
rs = stmt.executeQuery(sql); //执行参数中传来的sql语句
if (rs.next()) //判断结果集是否为空
k++; //结果集记录数
} catch (Exception e) {
k = -1;
close();
}
close();
return k;
}
public int update(String sql) { //数据库跟新方法
int k = -10;
init(getConn()); //初始化、获取连接
try {
k = 0;
k = stmt.executeUpdate(sql); //执行sql语句
} catch (Exception e) {
k = -1;
}
close();
return k;
}
public static void main(String[] args)throws Exception { //主函数，用于测试
DBConn db = new DBConn();
/**
* ��ȡ���ӵ���ݿ����
*/
System.out.println(db.getConn().getCatalog()); //测试连接是否成功
}
public static String getDate() {
return new SimpleDateFormat("yyyy-MM-dd hh-mm-ss").format(Calendar //时间转换
.getInstance().getTime());
}
public String chStr(String str) {
String temp2;
byte temp[] = null;
try {
temp = str.getBytes("ISO8859-1");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
temp2 = new String(temp);
return temp2;
}
public ResultSet query(String sql) { //查询测试
init(getConn());
try {
rs = stmt.executeQuery(sql);
} catch (Exception e) {
}
return rs;
}
}

Answer 3

没有悬赏啊，这个用的JDBC，连接的本地3306端口word服务器，用户名和密码都是root