JDBC基本操作
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| create table user(
id int primary key auto_increment,
name varchar(50)
) ENGINE = InnoDB DEFAULT CHARSET = utf8;
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JDBC概念
JDBC是一个独立于特定数据库管理系统、通用的SQL数据库存取和操作的公共接口，定义了用来访问数据库的标准的Java类库
连接步骤
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private static final String DRIVER = "com.mysql.jdbc.Driver";
private static final String URL = "jdbc:mysql://localhost:3306/test";
private static final String USER_NAME = "root";
private static final String PSW = "123456";
public static Connection getConnection(){
Connection conn = null;
try {
Class.forName(DRIVER);
conn = DriverManager.getConnection(URL,USER_NAME,PSW);
} catch (ClassNotFoundException e) {
System.out.println("加载驱动失败，请检查是否引入Jar包或者驱动名称是否正确");
throw new RuntimeException("加载驱动失败，请检查是否引入Jar包或者驱动名称是否正确",e);
} catch (SQLException throwables) {
System.out.println("连接数据库失败，请检查数据库地址，用户名，密码是否正确");
throw new RuntimeException("连接数据库失败，请检查数据库地址，用户名，密码是否正确",throwables);
}
return conn;
}
public static void close(Connection conn){
if(conn != null){
try {
conn.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
}
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注意：为什么需要使用Class.forName()来加载数据库驱动
是因为在每个Driver中都包含有一个静态代码块，实际调用的是DriverManager.registerDriver(new Driver());方法
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| public class Driver extends NonRegisteringDriver implements java.sql.Driver {
public Driver() throws SQLException {
}
static {
try {
DriverManager.registerDriver(new Driver());
} catch (SQLException var1) {
throw new RuntimeException("Can't register driver!");
}
}
}
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DriverManager
该类进行数据库驱动的管理，可以注册多个数据库驱动，根据url来动态的选择不同的数据库连接。
操作数据库
Statement接口
使用Statement接口来操作静态的SQL语句
executeUpdate方法
添加
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public static void doInsert(String sql){
Connection conn = getConnection();
Statement statement = null;
try {
statement = conn.createStatement();
int result = statement.executeUpdate(sql);
System.out.println(sql+"执行成功，插入"+result+"条数据");
} catch (SQLException e) {
throw new RuntimeException("执行失败",e);
} finally {
if(statement != null){
try {
statement.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
close(conn);
}
}
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修改
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public static void doUpdate(String sql){
Connection conn = getConnection();
Statement statement = null;
try {
statement = conn.createStatement();
int result = statement.executeUpdate(sql);
System.out.println(sql+"执行成功，修改"+result+"条数据");
} catch (SQLException e) {
throw new RuntimeException("执行失败",e);
} finally {
if(statement != null){
try {
statement.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
close(conn);
}
}
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删除
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public static void doDelete(String sql){
Connection conn = getConnection();
Statement statement = null;
try {
statement = conn.createStatement();
int result = statement.executeUpdate(sql);
System.out.println(sql+"执行成功，删除"+result+"条数据");
} catch (SQLException e) {
throw new RuntimeException("执行失败",e);
} finally {
if(statement != null){
try {
statement.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
close(conn);
}
}
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PreparedStatement接口
该接口为Statement的子接口，属于预处理操作，可以传入带有占位符的SQL，然后再进行补充占位符，索引值从1开始。
可以有效地防止SQL注入
executeUpdate方法
插入
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| public static void doPreparedInsert(String name){
Connection conn = getConnection();
PreparedStatement statement = null;
try {
String sql = "insert into user (name) values (?)";
statement = conn.prepareStatement(sql);
statement.setString(1,name);
int result = statement.executeUpdate();
System.out.println(sql+"执行成功，插入"+result+"条数据");
} catch (SQLException e) {
throw new RuntimeException("执行失败",e);
} finally {
if(statement != null){
try {
statement.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
close(conn);
}
}
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在创建preparedStatement对象时，有一个重载方法
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PreparedStatement prepareStatement(String sql, int autoGeneratedKeys)
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在使用该PreparedStatement执行插入操作时，可以使用statement.getGeneratedKeys()来返回一个新生成主键的ResultSet对象，结果集中只有一列GENERATED_KEY，存放的新生成的主键值
更新
与插入类似
删除
与插入类似
结果集
在查询数据时，返回的是一个二维的结果集，使用ResultSet来遍历结果集
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| public static void doQuery(){
String sql = "select * from user";
Connection conn = getConnection();
PreparedStatement statement = null;
ResultSet resultSet = null;
try {
statement = conn.prepareStatement(sql);
resultSet = statement.executeQuery();
while (resultSet.next()){
int id = resultSet.getInt("id");
String name = resultSet.getString("name");
System.out.println("查询到id为"+id+",name为"+name+"的记录");
}
} catch (SQLException throwables) {
throwables.printStackTrace();
} finally {
if(resultSet != null){
try {
resultSet.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
close(conn,statement);
}
}
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批量操作
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| public static void doBatchInsert(String sql){
Connection conn = getConnection();
PreparedStatement statement = null;
try {
statement = conn.prepareStatement(sql);
for(int i = 0;i<1000;i++){
statement.setString(1,"张三"+i);
statement.addBatch();
}
statement.executeBatch();
statement.clearBatch();
} catch (SQLException throwables) {
throwables.printStackTrace();
} finally {
close(conn,statement);
}
}
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