jdbc03.使用Statement 接口实现增/删/改操作

快捷键：Ctrl+Shift+f，将长句自动分段

- Statement 接口

作用：用于执行静态SQL 语句并返回它所生成结果的对象。

int executeUpdate(String sql) 执行给定SQL 语句，该语句可能为INSERT、UPDATE 或DELETE 语句，或者不返回任何内容的SQL 语句（如SQL DDL 语句）。

void close() 立即释放此Statement 对象的数据库和JDBC 资源，而不是等待该对象自动关闭时发生此操作

实例化Statement 接口 使用接口 Statement页面的另外参见Connection.createStatement(), 如下图

public class Demo1 {

public static void main(String[] args) throws Exception {
String sql = "insert into t_student values(null, 'bob', '23', '男','六年级')";//此处用''t_student 为db_book里的表，null表示插在后面

DbUtil dbUtil = new DbUtil();
Connection con = dbUtil.getCon();//获取数据库连接
Statement stat = con.createStatement();
int result = stat.executeUpdate(sql);//返回更新的数据条数
stat.close();//关闭Statement
con.close();//关闭连接//先打开的后关闭
System.out.println("操作了："+ result +"条数据");

}
}

添加数据

/**
* 用于封装数据库连接的一些方法
* @author Gavin
*
*/
public class DbUtil {

private static String jdbcName = "com.mysql.jdbc.Driver";//驱动名字，不能随便改
private static String dbUrl = "jdbc:mysql://localhost:3306/db_book";//mysql的数据库地址
public static String dbUserName = "root";//数据库用户名
public static String dbPassWord = "123456";//密码
/**
* 获取数据库连接
* @return
* @throws Exception
*/
public Connection getCon() throws Exception {
Class.forName(jdbcName);
Connection con = DriverManager.getConnection(dbUrl, dbUserName, dbPassWord);
return con;
}
/**
* 关闭连接
* @param con
* @throws Exception
*/
public void closeCon(Statement stat,Connection con) throws Exception {
if(stat!=null){
stat.close();
if (con!=null){
con.close();
}
}

}
}

输出：操作了1条数据

数据库如下图


数据类型如下



封装上面添加数据的方法,功能一样

/**
* 用来将student对象封装
* @author Gavin
*
*/
public class Student
ba58
{

//alt+S生成构造函数
public Student(String stuName, double age, String sex, String gradeName) {
super();
this.stuName = stuName;
this.age = age;
this.sex = sex;
this.gradeName = gradeName;
}
private  String stuName;
private double age;
private String sex;
private String gradeName;
public String getStuName() {
return stuName;
}
public void setStuName(String stuName) {
this.stuName = stuName;
}
public double getAge() {
return age;
}
public void setAge(double age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getGradeName() {
return gradeName;
}
public void setGradeName(String gradeName) {
this.gradeName = gradeName;
}
}

public static DbUtil dbUtil = new DbUtil();

private static int addStudent2(Student student) throws Exception {
String sql = "insert into t_student values(null, '"+student.getStuName()+"', '"+student.getAge()+"', '"+student.getSex()+"', '"+student.getGradeName()+"')";
Connection con = dbUtil.getCon();
Statement stat = con.createStatement();
int result = stat.executeUpdate(sql);
dbUtil.closeCon(stat, con);
if (result == 1){
System.out.println("添加成功");
}
return result;

}

public static void main(String[] args) throws Exception {
/*addStudent("张三",   12, "男", "大二");*/
Student student = new Student("张三",  12, "男", "大san");
addStudent2(student);
}
}

更新数据

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;

import com.jdbc03.model.Student;
import com.jdbc03.util.DbUtil;

public class Demo3 {

private static DbUtil dbUtil = new DbUtil();

private static int updateStudent(Student student) throws Exception {
String sql = "update t_student set stuName = '" + student.getStuName()
+ "', age = " + student.getAge() + ", sex = '"
+ student.getSex() + "', gradeName = '"
+ student.getGradeName() + "' where id = " + student.getId();
//注意此处写法stuName，age，gradeName等为数据库表中的项目，Ctrl+Shift+F：将长句子分段
Connection con = dbUtil.getCon();
Statement stat = con.createStatement();
int result = stat.executeUpdate(sql);
dbUtil.closeCon(stat, con);

return result;
}

public static void main(String[] args) throws Exception {

Student student = new Student(6, "we", 22, "女", "233");
int result = updateStudent(student);
if(result == 1){
System.out.println("成功");
}

}
}

/**
* 用来将student对象封装
* @author Gavin
*
*/
public class Student {
private int id;
private  String stuName;
private double age;
private String sex;
private String gradeName;
//alt+S生成构造函数
public Student(String stuName, double age, String sex, String gradeName) {
super();
this.stuName = stuName;
this.age = age;
this.sex = sex;
this.gradeName = gradeName;
}

//由于更改需要用到id，所以需要重载构造函数 alt+S
public Student(int id, String stuName, double age, String sex,
String gradeName) {
super();
this.id = id;
this.stuName = stuName;
this.age = age;
this.sex = sex;
this.gradeName = gradeName;
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public String getStuName() {
return stuName;
}
public void setStuName(String stuName) {
this.stuName = stuName;
}
public double getAge() {
return age;
}
public void setAge(double age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getGradeName() {
return gradeName;
}
public void setGradeName(String gradeName) {
this.gradeName = gradeName;
}

}

删除

import java.sql.Connection;
import java.sql.Statement;

import com.jdbc03.model.Student;
import com.jdbc03.util.DbUtil;

public class Demo4 {

private static DbUtil dbUtil = new DbUtil();
private static int delectStu(int id) throws Exception {
Connection con = dbUtil.getCon();
String sql = "delete from t_student where id = " +id;//此处用''
Statement stat = con.createStatement();//创建Statement
int result = stat.executeUpdate(sql);
dbUtil.closeCon(stat, con);
return result;
}

public static void main(String[] args) throws Exception {
int result = delectStu(3);
if(result == 1){
System.out.println("删除成功");
}
}
}