文章目录
效果预览
提供同一个包下的两个类(可以作为模板）
public class ConnectMySql（封装了不少方法）
package sql;
import java.sql.*;
/**
* 使用本类最好不要用匿名对象（否则不易关闭connection）
*/
public class ConnectMySql {
/*成员变量*/
//根据需要将url,user,password改为自己相应的值
static String url = "jdbc:mysql://10.21.6.18/OnlineShoppingSystem?useSSL=FALSE&serverTimezone=UTC";
static String user = "oss";
static String password = "onlinss";
static Connection connection;
final static String driver = "com.mysql.cj.jdbc.Driver";
/*提供ps成员变量以便于关闭*/
PreparedStatement ps;
ResultSet rs;
/*constructor to connect the database (this operation will get a Connection object*/
public ConnectMySql() {
//注册驱动
try {
Class.forName(driver);
/*在构造方法中直接尝试连接数据库*/
connection = DriverManager.getConnection(url, user, password);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
//提供链接数据库的方法的接口(通用)
public Connection getConnection() {
//System.out.println("数据库连接成功(记得操作完毕关闭接口)");
/*connection.close()*/
return connection;
}
/* //得到执行sql语句的Statement对象(statement:表示sql的查询语句.)
System.out.println("数据库连接成功");
Statement stmt = conn.createStatement();//得到具有执行sql语句的功能的对象*/
/**
* getStatement()
* 得到具有执行sql语句的功能的对象(但更多的是直接使用getConnection()方法(以便在外部使用PrepareStatement)
*/
public Statement getStatement() throws SQLException {
//ConnectMySql connectMySql=new ConnectMySql();
Statement statement = getConnection().createStatement();//得到具有执行sql语句的功能的对象*/
return statement;
}
/**
* 使用了（或间接使用了本方法）请调用closePreparedStatement()或者closeAll()方法。
*
* @param sql
* @return
* @throws SQLException
*/
public PreparedStatement getPreparedStatement(String sql) throws SQLException {
return ps = getConnection().prepareStatement(sql);
}
/**
* 获取查询结果ResultSet对象
*
* @param sql
* @return
* @throws SQLException
*/
public ResultSet getResultSet(String sql) throws SQLException {
/*调用PreparedStatement类中的executeQuery()方法来获取中要ResultSet类的对象rs*/
return getPreparedStatement(sql).executeQuery();
}
public ResultSetMetaData getResultSetMetaData(String sql) throws SQLException {
return getResultSet(sql).getMetaData();
}
/**
* 获取查询返回结果的列数（本方法不易反复调用）
*
* @param sql
* @return
* @throws SQLException
*/
public int getColumnSize(String sql) throws SQLException {
/*获得ResultSetMetaData对象(元数据对象),(这一对象是jdbc中的关键对象),以进一步获取列数*/
ResultSetMetaData resultSetMetaData = getResultSetMetaData(sql);
return resultSetMetaData.getColumnCount();
}
public String getColumnNames(String tableName) throws SQLException {
String sqlColumns = "select * from " + tableName;
StringBuilder stringBuilder = new StringBuilder();
ResultSetMetaData resultSetMetaData = getResultSetMetaData(sqlColumns);
int columnSize = resultSetMetaData.getColumnCount();
for (int i = 1; i <= columnSize; i++) {
/*从元数据对象获取列名(调用方法getColumnName(i))
* 注意:getColumnName是用来从ResultSetMetaData对象中获取各个字段(属性)的名称,
* 而不是字段的值*/
// System.out.printf("%-12s", resultSetMetaData.getColumnName(i));
stringBuilder.append(resultSetMetaData.getColumnName(i) + "\t");
}
return stringBuilder.toString();
}
public void printColumnNames(String sql) throws SQLException {
// System.out.println("查询字段名结果如下:");
//通过获取ResultMetaData对象，再获取列数(字段数),以打印字段名
ResultSetMetaData resultSetMetaData = getResultSetMetaData(sql);
int columnSize = resultSetMetaData.getColumnCount();
for (int i = 1; i <= columnSize; i++) {
/*从元数据对象获取列名(调用方法getColumnName(i))
* 注意:getColumnName是用来从ResultSetMetaData对象中获取各个字段(属性)的名称,
* 而不是字段的值*/
System.out.printf("%-20s", resultSetMetaData.getColumnName(i));
}
System.out.println();
}
public void printSearchResult(String sql) throws SQLException {
ResultSet resultSet = getResultSet(sql);
/*打印所有记录*/
//建议将columnSize在循环外计算一下并记住，以避免在for中重复计算。
int columnSize = getColumnSize(sql);
while (resultSet.next()) {
for (int i = 1; i <= columnSize; i++) {
/*这里调用的是getObject(i)来打印出各种类型的各字段的值*/
System.out.printf("%-20s", resultSet.getObject(i));
// System.out.print("\t\t"+resultSet.getObject(i));
}
System.out.println();
}
//System.out.println();
System.out.println("\n结束查询");
}
/*测试方法*/
public static void main(String[] args) throws SQLException {
ConnectMySql connectMySql = new ConnectMySql();
System.out.println(connectMySql.getColumnNames("Goods"));
connectMySql.closeConnection();
}
/* public void closeResultSet(String sql) throws SQLException {
getResultSet(sql).close();
}*/
/**
* 提供关闭数据库链接的接口
*/
public void closeConnection() {
try {
if (connection != null) {
connection.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
/* public void closeStatement(){
}*/
public void closePreparedStatement() {
try {
if (ps != null) {
ps.close();
}
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
public void closeResultSet() {
try {
if (rs != null) {
rs.close();
}
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
public void closeAll() {
closeResultSet();
closePreparedStatement();
closeConnection();
}
}
public class UseMySql（封装了增删改查的方法（依赖于上一个类ConnectMySql））
package sql;
import java.sql.*;
import java.util.Scanner;
/**
* @Author xuchaoxin
* @Date 2021/1/23 22:35
* @Version 1.0
* the detail and improved version(if I update it ) to see:
* the github repository (search the article):https://github.com/xuchaoxin1375/LearnJava
*/
public class UseMySql {
/*统一输入流对象*/
static Scanner scanner = new Scanner(System.in);
/*统一链接对象*/
static ConnectMySql connectMySql = new ConnectMySql();
public static void search() throws SQLException {
System.out.println("testing...");
ConnectMySql connectMySql = new ConnectMySql();
System.out.println("输入sql查询语句:示例:select * from Goods where kid=2");
Scanner scanner = new Scanner(System.in);
String sqlSearch = scanner.nextLine();
/*对查询结果进行处理并打印出来:*/
try {
/*由于我将sql查询的字段名称的打印方法封装到了ConnectMySql，故可一键打印。*/
connectMySql.printColumnNames(sqlSearch);
connectMySql.printSearchResult(sqlSearch);
} catch (Exception e) {
e.printStackTrace();
} finally {
//关闭顺序: ResultSet-->(Prepared)Statement-->Connection
connectMySql.closeAll();
}
}
public static void simpleSearch() throws SQLException {
/* System.out.println("输入要查询表:示例:Kinds");
Scanner scanner = new Scanner(System.in);
String table=scanner.nextLine();
*/
System.out.println("将执行类似于：select g_name,k_name from The_goods_a where kid='06'的查询动作");
Scanner scanner = new Scanner(System.in);
System.out.println("输入需要查询的表:示例:The_goods_a");
String tables = scanner.nextLine();
/*查找视图字典:*/
String[] tableArray = tables.split(" ");
for (String tableName : tableArray) {
//sqlDictionary.getInformation(tableName);
System.out.println("申请被插入的视图的信息...");
System.out.println(connectMySql.getColumnNames(tableName));
}
try {
//查询语句
//String sql1 = "select * from Goods";
//System.out.println("简单查询:示例:select * from Goods where kid=2");
//String sqlSearch="select * from "+table+" where kid=2";
/*交互阶段:*/
System.out.println("输入需要查询的字段(逗号分隔不同字段):例如:Gid,GName");
String columns = scanner.nextLine();
System.out.println("输入需本次查询需要满足的条件(注意要由where引出条件:示例:where kid=2");
String where = scanner.nextLine().trim();
String sqlSearch = "select " + columns + " from " + tables + " " + where;
System.out.println("将执行" + sqlSearch);
/*开始处理sql命令*/
System.out.println("查询结果如下:");
connectMySql.printColumnNames(sqlSearch);
connectMySql.printSearchResult(sqlSearch);
} finally {
connectMySql.closeAll();
}
}
public static void simpleSearchTable() throws SQLException {
System.out.println("输入要查询表:示例:Kinds");
Scanner scanner = new Scanner(System.in);
String table = scanner.nextLine();
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
String sql1 = "select * from " + table;
//ps = conn.prepareStatement(sql1);
ps = new ConnectMySql().getPreparedStatement(sql1);
rs = ps.executeQuery();
//获取列数
ResultSetMetaData md = rs.getMetaData();
int columnSize = md.getColumnCount();
System.out.println("查询结果如下:");
//打印字段名
for (int i = 1; i <= columnSize; i++) {
System.out.printf("%-12s", md.getColumnName(i));
}
System.out.println();
//打印所有记录
while (rs.next()) {
for (int i = 1; i <= columnSize; i++) {
System.out.printf("%-12s", rs.getObject(i));
}
System.out.println();
}
System.out.println("\n结束查询");
//关闭顺序: ResultSet-->Statement-->Connection
try {
if (rs != null) {
rs.close();
}
} catch (Exception e) {
e.printStackTrace();
}
try {
if (ps != null) {
ps.close();
}
} catch (Exception e) {
e.printStackTrace();
}
try {
if (conn != null) {
conn.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
public static void insert() throws SQLException {
//SimpleSearch.simpleSearch();
System.out.println("输入插入语句:示例:insert into Kinds values('13','hhh')");
Scanner scanner = new Scanner(System.in);
//插入语句示例:insert into Kinds values('13','hhh')
String insertSql = scanner.nextLine();
/*PreparedStatement extends Statement
* 执行插入语句:(示例语句:
* 插入语句示例:insert into Kinds values('13','hhh')
*/
PreparedStatement preparedStatement = connectMySql.getConnection().prepareStatement(insertSql);
/*采用execute()方式执行语句*/
preparedStatement.execute();
System.out.println("插入成功.");
}
public static void simpleInsert() throws SQLException {
//SimpleSearch.simpleSearch();
System.out.println("简单插入模式:");
Scanner scanner = new Scanner(System.in);
Scanner scanner1 = new Scanner(System.in);
//插入语句示例:insert into Kinds values('13','hhh')
String insertPrefix = "insert into";
// String insertSql = scanner.nextLine();
System.out.println("输入被插入的表:");
String table = scanner.nextLine();
//new SqlDictionary().getInformation(table);
System.out.println("申请被插入的视图的信息...");
System.out.println(connectMySql.getColumnNames(table));
System.out.println("输入values(形如values('13','hhh'):");
String values = scanner1.nextLine();
/*关闭流：*/
scanner.close();
scanner1.close();
String insertSql = "insert into " + table.trim() + " " + values;
/*PreparedStatement extends Statement
* 执行插入语句:(示例语句:
* 插入语句示例:insert into Kinds values('13','hhh')
*/
PreparedStatement preparedStatement = connectMySql.getConnection().prepareStatement(insertSql);
/*采用execute()方式执行语句*/
preparedStatement.execute();
}
public static void update() throws SQLException {
System.out.println("输入更新语句sql:示例:update Admin set AName='ju' where Aid='111'");
/* 语句示例:update Admin set AName='ju' where Aid='111'*/
String updateSql = scanner.nextLine();
PreparedStatement preparedStatement = connectMySql.getConnection().prepareStatement(updateSql);
preparedStatement.execute();
System.out.println("修改/更新成功");
}
public static void simpleUpdate() throws SQLException {
System.out.println("简单修改模式：");
System.out.println("输入要更新(修改)的表名");
/*只有一个Scanner不便二次读入*/
Scanner scanner = new Scanner(System.in);
String table = scanner.nextLine();
//scanner.close();
new SqlDictionary().getInformation(table);
System.out.println("输入待修改的字段('='号形式）:(形如:AName='ju')");
String columnModify = scanner.next().trim();
System.out.println("输入修改条件:形如:where Aid='111' ");
Scanner scanner1 = new Scanner(System.in);
String where = scanner1.nextLine();
// scanner1.close();
String updateSql = "update " + table + " set " + columnModify + " " + where;
System.out.println("testing...");
PreparedStatement preparedStatement = connectMySql.getConnection().prepareStatement(updateSql);
preparedStatement.execute();
System.out.println("修改/更新成功");
}
public static void simpleDelete() throws SQLException {
Scanner scanner = new Scanner(System.in);
Scanner scanner1 = new Scanner(System.in);
System.out.println("简单删除:");
System.out.println("输入要被删除记录的表:");
String table = scanner.nextLine();
/*提示该表具有的字段。*/
//new SqlDictionary().getInformation(table);
System.out.println(connectMySql.getColumnNames(table));
System.out.println("输入where(形如:where Aid='234')");
String where = scanner1.nextLine().trim();
scanner.close();
scanner1.close();
/*示例: delete from Admin where Aid='234'*/
String deleteSql = "delete from " + table + " " + where;
PreparedStatement preparedStatement = connectMySql.getConnection().prepareStatement(deleteSql);
preparedStatement.execute();
System.out.println("删除成功");
}
public static void delete() throws SQLException {
System.out.println("输入sql删除语句:示例: delete from Admin where Aid='234'");
/*示例: delete from Admin where Aid='234'*/
String deleteSql = scanner.nextLine();
PreparedStatement preparedStatement = connectMySql.getConnection().prepareStatement(deleteSql);
preparedStatement.execute();
System.out.println("删除成功");
}
public static void printUsingHelp() {
//todo
System.out.println("管理员Admin（管理员ID Aid，姓名 AName，电话 APhone，账号AAccount，密码APwd,等级Level）\n" +
"主键：Aid 外键：Level\n" +
"权限Permission(等级 Level,权限名 PName,说明 Illustration)\n" +
"主键：Level\n" +
"管理Manage（管理员ID Aid，商品ID Gid，操作日志 Record,操作时间 MTime）\n" +
"主键：Gid和Aid 外键 Aid、Gid\n" +
"商品Goods（商品名Gname，促销 Sale，库存Repertory，销量 Snumber，图片Picture，简介Introduce，商品ID Gid,品类ID Kid，发货地 Gaddress，售价 Sprice,进价Pprice,状态Gstatus）\n" +
"主键：Gid 外键：Kid\n" +
"购物车Shopcart（购物车ID Sid,客户ID Cid，商品数量 Cnumber）\n" +
"主键：Sid和Cid 外键：Sid、Cid\n" +
"客户Customer（电话Cphone，地址Caddress，余额Balance，客户ID Cid,性别Csex，姓名Cname,账号Caccount，密码Cpwd）\n" +
"主键：Cid \n" +
"订单Orders（订单号Oid，状态OStatus，下单时间Otime，客户ID Cid,商品ID Gid，商品数量 Gnumber，运费 Fare，备注：Remarks）\n" +
"主键：Oid 外键：Gid，Cid\n" +
"商品品类Kind（品类名 Kname，品类ID Kid）\n" +
"主键:Kid\n" +
"评论Discuss（商品Gid ,客户ID Cid ,评论ID Did，评论内容 Content，评论时间 Dtime）主键：Did 外键：Gid、Cid");
}
/* connectMySql.closeConnection();*/
/*测试用的main*/
public static void main(String[] args) throws SQLException {
//delete();
//insert();
// update();
//simpleDelete();
simpleSearch();
//simpleDelete();
// search();
}
}
// System.out.println();
//处理结果
/* while (rs.next()) {
*//*遍历各条记录的各个字段(比如goods表有五个字段*//*
for(int i=1;i<=7;i++){
System.out.print(rs.getString(i++) + "\t");
}
System.out.println();
}*/