Java泛型与数据库应用实例详解

2019-11-26 08:44:55

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本文实例讲述了Java泛型与数据库应用。分享给大家供大家参考，具体如下：

一点睛

BaseDao定义了基本的数据库增删查改，之后可以继承该泛型类，实现各自的增删查改，或者使用超类的增删查改，同时每个继承类还能增加自己的操作。

二实战

1 BaseDao.java

import java.lang.reflect.Field;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;public class BaseDao<T> {  Connection connection;  PreparedStatement pStatement;  String urlString = "jdbc:mysql://localhost:3306/student?useUnicode=true&characterEncoding=UTF8";  String drivString = "com.mysql.jdbc.Driver";  void OpenDB() {    try {      if (connection == null) {        Class.forName(drivString);        this.connection = DriverManager.getConnection(urlString, "root", "123456");      }    } catch (Exception e) {      e.printStackTrace();    }  }  void CloseDB() {    try {      if (pStatement != null) pStatement.close();      if (connection != null) connection.close();    } catch (Exception e) {      e.printStackTrace();    }  }  public void Save( T t ) {    OpenDB();    String table = "";    String sqlString = "insert into ";    try {      table = t.getClass().getSimpleName();      Field[] fields = t.getClass().getDeclaredFields();      sqlString += table;      String sqlNameString = "";      String sqlValString = "";      for (Field field : fields) {        sqlNameString += field.getName() + ",";        sqlValString += "?,";      }      sqlNameString = sqlNameString.substring(0, sqlNameString.length() - 1);      sqlValString = sqlValString.substring(0, sqlValString.length() - 1);      pStatement = connection.prepareStatement(sqlString + " (" + sqlNameString + ") values (" + sqlValString + ")");      int n = 1;      for (Field field : fields) {        field.setAccessible(true);        System.out.println(field.get(t).toString());        pStatement.setString(n, field.get(t).toString());        n++;      }      pStatement.executeUpdate();      CloseDB();    } catch (Exception e) {      e.printStackTrace();      CloseDB();    }  }  public void Del( T t ) {  }  public void Update( T t ) {  }  public void Search( T t ) {  }}

2 StudentDao.java

public class StudentDao extends BaseDao<Student> {}

3 TeacherDao.java

public class TeacherDao extends BaseDao<Teacher> {}

4 Student.java

public class Student {  public String name;  public int age;  public String dept;  /**  * @return the name  */  public String getName() {   return name;  }  /**  * @param name the name to set  */  public void setName(String name) {   this.name = name;  }  /**  * @return the age  */  public int getAge() {   return age;  }  /**  * @param age the age to set  */  public void setAge(int age) {   this.age = age;  }  /**  * @return the dept  */  public String getDept() {   return dept;  }  /**  * @param dept the dept to set  */  public void setDept(String dept) {   this.dept = dept;  }}

5 Teacher.java

public class Teacher {}

6 TestDao.java

public class TestDao {  public static void main(String[] args) {   System.out.println("ok");   Student stud=new Student();   stud.age=20;   stud.name="zhangsan";   stud.dept="computer";   StudentDao sd=new StudentDao();   sd.Save(stud);   System.out.println(stud.dept);  }}

三运行

ok
zhangsan
20
computer
computer

四怎样在IDEA中导入jar包

可参考附录：IDEA连接数据库（导入jar包）

五另外一种写法

StudentDao.java

public class StudentDao<M> extends BaseDao<M> {    // 这里的M可以是任意合法标识符}

TestDao.java

public class TestDao { public static void main(String[] args) { System.out.println("ok"); Student stud=new Student(); stud.age=20; stud.name="zhangsan2"; stud.dept="computer"; StudentDao<Student> sd=new StudentDao<>();  // 这里要说明是Student sd.Save(stud); System.out.println(stud.dept); TeacherDao<Teacher> te= new TeacherDao<>(); }}

附：IDEA连接数据库（导入jar包）

Java连接 MySQL 需要驱动包，最新版下载地址为：http://dev.mysql.com/downloads/connector/j/，解压后得到jar库文件，然后在对应的项目中导入该库文件。

IDEA导入jar过程:新建文件夹（名称任意，这里使用Lib）,导入mysql-connector-java-*.*.**-bin.jar如下图