JDBC 数据库连接

4. 曾删改查方法

public class SaveOrUpdate {
	@Test
	public void save(){
		Connection conn = null;
		Statement stmt = null;
		try {
			conn = JDBCUtils.getConnection();
			stmt = conn.createStatement();
			String sql = "insert into student(name,gender)values(‘波多野结衣妹子‘,‘女‘)";
			int count = stmt.executeUpdate(sql);
			System.out.println(count);
		} catch (Exception e) {
			throw new RuntimeException(e);
		}finally{
			JDBCUtils.close(stmt, conn);
		}
	}
	
	//注意:1. update table student报错,只能写update student!!!!  
	//如:"UPDATE student SET NAME=‘瑶瑶‘, gender=‘女‘ WHERE id = ‘2‘ AND NAME=‘zhangsan‘"
	//2. set多个值时候只能用逗号隔开不能用and隔开!!!!
	@Test
	public void update(){
		Connection conn = null;
		Statement stmt = null;
		try {
			conn = JDBCUtils.getConnection();
			stmt = conn.createStatement();
			String sql = "UPDATE student SET NAME=‘我爱瑶瑶‘, gender=‘女‘ WHERE id =2";
			stmt.executeUpdate(sql);
		} catch (Exception e) {
			throw new RuntimeException(e);
		}finally{
			JDBCUtils.close(stmt, conn);
		}
	}
	
	@Test
	public void delete(){
		Connection conn = null;
		Statement stmt = null;
		try {
			conn = JDBCUtils.getConnection();
			stmt = conn.createStatement();
			String sql = "delete from student WHERE id =2";
			stmt.executeUpdate(sql);
		} catch (Exception e) {
			throw new RuntimeException(e);
		}finally{
			JDBCUtils.close(stmt, conn);
		}
	}
	
	public List<Student> findAll(){
		Connection conn = null;
		Statement stmt = null;
		
		try {
			conn = JDBCUtils.getConnection();
			stmt = conn.createStatement();
			String sql = "SELECT * FROM STUDENT";
			ResultSet resultSet = stmt.executeQuery(sql);
			List<Student> studentList = new ArrayList<>();
			while(resultSet.next()){
				Student student = new Student();
				student.setId(resultSet.getInt("id"));//列名必须与数据库的字段一样但不区分大小写
				student.setName(resultSet.getString("NAME"));
				student.setGender(resultSet.getString("GeNdEr"));
				studentList.add(student);
			}
			return studentList;
		} catch (SQLException e) {
			throw new RuntimeException(e);
		}
	}
	
	@Test
	public void iterate(){
		List<Student> studentList = findAll();
		for(Student stu : studentList){
			System.out.println(stu.getId()+"***"+stu.getName()+"****"+stu.getGender());
		}
	}
}

	class Student{
		private int id;
		private String name;
		private String gender;
		
		public Student() {}
		public int getId() {
			return id;
		}
		public void setId(int id) {
			this.id = id;
		}
		public String getName() {
			return name;
		}
		public void setName(String name) {
			this.name = name;
		}
		public String getGender() {
			return gender;
		}
		public void setGender(String gender) {
			this.gender = gender;
		}
		@Override
		public String toString() {
			return "Student [id=" + id + ", name=" + name + ", gender="
					+ gender + "]";
		}
	}

JDBC 数据库连接

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