简单通用JDBC辅助类封装(实例)

package com.tly.dbutil;import java.io.IOException;import java.util.Properties;public class Config {  private static Properties prop = new Properties();    static{        try {      //加载dbconfig.properties配置文件      prop.load(Config.class.getResourceAsStream("dbconfig.properties"));    } catch (IOException e) {      // TODO Auto-generated catch block      e.printStackTrace();    }  }    //设置常量  public static final String CLASS_NAME = prop.getProperty("CLASS_NAME");  public static final String DATABASE_URL = prop.getProperty("DATABASE_URL");  public static final String SERVER_IP = prop.getProperty("SERVER_IP");  public static final String SERVER_PORT = prop.getProperty("SERVER_PORT");  public static final String DATABASE_SID = prop.getProperty("DATABASE_SID");  public static final String USERNAME = prop.getProperty("USERNAME");  public static final String PASSWORD = prop.getProperty("PASSWORD");  }

CLASS_NAME=com.mysql.jdbc.DriverDATABASE_URL=jdbc:mysqlSERVER_IP=localhostSERVER_PORT=3306DATABASE_SID=employeesUSERNAME=rootPASSWORD=1

package com.employees.dbutil;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;public class DBConn {  //三属性、四方法    //三大核心接口  private Connection conn = null;  private PreparedStatement pstmt = null;  private ResultSet rs = null;    //四个方法  //method1: 创建数据库的连接  public Connection getConntion(){        try {      //1: 加载连接驱动，Java反射原理      Class.forName(Config.CLASS_NAME);      //2:创建Connection接口对象，用于获取MySQL数据库的连接对象。三个参数：url连接字符串  账号 密码      String url = Config.DATABASE_URL+"://"+Config.SERVER_IP+":"+Config.SERVER_PORT+"/"+Config.DATABASE_SID;      conn = DriverManager.getConnection(url,Config.USERNAME,Config.PASSWORD);    } catch (ClassNotFoundException e) {      e.printStackTrace();    } catch (SQLException e) {      e.printStackTrace();    }      return conn;  }      //method2：关闭数据库的方法  public void closeConn(){    if(rs!=null){      try {        rs.close();      } catch (SQLException e) {        e.printStackTrace();      }    }    if(pstmt!=null){      try {        pstmt.close();      } catch (SQLException e) {        e.printStackTrace();      }    }    if(conn!=null){      try {        conn.close();      } catch (SQLException e) {        e.printStackTrace();      }    }  }    //method3: 专门用于发送增删改语句的方法  public int execOther(PreparedStatement pstmt){    try {      //1、使用Statement对象发送SQL语句      int affectedRows = pstmt.executeUpdate();      //2、返回结果      return affectedRows;    } catch (SQLException e) {      e.printStackTrace();      return -1;    }  }  //method4: 专门用于发送查询语句  public ResultSet execQuery(PreparedStatement pstmt){    try {      //1、使用Statement对象发送SQL语句      rs = pstmt.executeQuery();      //2、返回结果      return rs;    } catch (SQLException e) {      e.printStackTrace();      return null;    }  }}

package com.employees.dao;import java.io.InputStream;import java.lang.reflect.Method;import java.lang.reflect.ParameterizedType;import java.sql.Connection;import java.sql.Date;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import com.employees.dbutil.DBConn;public class BaseDAO<T> {    DBConn conn = new DBConn();  private Connection connection = null;    @SuppressWarnings("unused")  private Class<T> persistentClass;    @SuppressWarnings("unchecked")  public BaseDAO() {    initConnection();    //获得参数化类型        ParameterizedType type = (ParameterizedType)getClass().getGenericSuperclass();    persistentClass = (Class<T>)type.getActualTypeArguments()[0];  }      /**   * 获得数据库连接   */  public void initConnection() {    connection = conn.getConntion();        }      /**   * 保存   */  public void save(T entity) throws Exception{    //SQL语句,insert into table name (    String sql = "insert into " + entity.getClass().getSimpleName().toLowerCase() + "(";        //获得带有字符串get的所有方法的对象    List<Method> list = this.matchPojoMethods(entity,"get");        Iterator<Method> iter = list.iterator();        //拼接字段顺序 insert into table name(id,name,email,    while(iter.hasNext()) {      Method method = iter.next();      sql += method.getName().substring(3).toLowerCase() + ",";    }        //去掉最后一个,符号insert insert into table name(id,name,email) values(    sql = sql.substring(0, sql.lastIndexOf(",")) + ") values(";        //拼装预编译SQL语句insert insert into table name(id,name,email) values(?,?,?,    for(int j = 0; j < list.size(); j++) {      sql += "?,";    }    //去掉SQL语句最后一个,符号insert insert into table name(id,name,email) values(?,?,?);    sql = sql.substring(0, sql.lastIndexOf(",")) + ")";        //到此SQL语句拼接完成,打印SQL语句    System.out.println(sql);        //获得预编译对象的引用    PreparedStatement statement = connection.prepareStatement(sql);        int i = 0;    //把指向迭代器最后一行的指针移到第一行.    iter = list.iterator();    while(iter.hasNext()) {      Method method = iter.next();      //此初判断返回值的类型,因为存入数据库时有的字段值格式需要改变,比如String,SQL语句是'"+abc+"'      if(method.getReturnType().getSimpleName().indexOf("String") != -1) {        statement.setString(++i, this.getString(method, entity));      } else if(method.getReturnType().getSimpleName().indexOf("Date") != -1){        statement.setDate(++i, this.getDate(method, entity));      } else if(method.getReturnType().getSimpleName().indexOf("InputStream") != -1) {        statement.setAsciiStream(++i, this.getBlob(method, entity),1440);      } else {        statement.setInt(++i, this.getInt(method, entity));      }    }    //执行    conn.execOther(statement);    //关闭连接    conn.closeConn();  }      /**   * 修改   */  public void update(T entity) throws Exception{    String sql = "update " + entity.getClass().getSimpleName().toLowerCase() + " set ";        //获得该类所有get方法对象集合    List<Method> list = this.matchPojoMethods(entity,"get");        //临时Method对象,负责迭代时装method对象.    Method tempMethod = null;        //由于修改时不需要修改ID,所以按顺序加参数则应该把Id移到最后.    Method idMethod = null;    Iterator<Method> iter = list.iterator();    while(iter.hasNext()) {      tempMethod = iter.next();      //如果方法名中带有ID字符串并且长度为2,则视为ID.      if(tempMethod.getName().lastIndexOf("Id") != -1 && tempMethod.getName().substring(3).length() == 2) {        //把ID字段的对象存放到一个变量中,然后在集合中删掉.        idMethod = tempMethod;        iter.remove();      //如果方法名去掉set/get字符串以后与pojo + "id"想符合(大小写不敏感),则视为ID      } else if((entity.getClass().getSimpleName() + "Id").equalsIgnoreCase(tempMethod.getName().substring(3))) {        idMethod = tempMethod;        iter.remove();              }    }        //把迭代指针移到第一位    iter = list.iterator();    while(iter.hasNext()) {      tempMethod = iter.next();      sql += tempMethod.getName().substring(3).toLowerCase() + "= ?,";    }        //去掉最后一个,符号    sql = sql.substring(0,sql.lastIndexOf(","));        //添加条件    sql += " where " + idMethod.getName().substring(3).toLowerCase() + " = ?";        //SQL拼接完成,打印SQL语句    System.out.println(sql);        PreparedStatement statement = this.connection.prepareStatement(sql);        int i = 0;    iter = list.iterator();    while(iter.hasNext()) {      Method method = iter.next();      //此初判断返回值的类型,因为存入数据库时有的字段值格式需要改变,比如String,SQL语句是'"+abc+"'      if(method.getReturnType().getSimpleName().indexOf("String") != -1) {        statement.setString(++i, this.getString(method, entity));      } else if(method.getReturnType().getSimpleName().indexOf("Date") != -1){        statement.setDate(++i, this.getDate(method, entity));      } else if(method.getReturnType().getSimpleName().indexOf("InputStream") != -1) {        statement.setAsciiStream(++i, this.getBlob(method, entity),1440);      } else {        statement.setInt(++i, this.getInt(method, entity));      }          }        //为Id字段添加值    if(idMethod.getReturnType().getSimpleName().indexOf("String") != -1) {      statement.setString(++i, this.getString(idMethod, entity));    } else {      statement.setInt(++i, this.getInt(idMethod, entity));    }        //执行SQL语句    statement.executeUpdate();                //关闭预编译对象        statement.close();                //关闭连接        connection.close();  }      /**   * 删除   */  public void delete(T entity) throws Exception{    String sql = "delete from " + entity.getClass().getSimpleName().toLowerCase() + " where ";        //存放字符串为"id"的字段对象    Method idMethod = null;        //取得字符串为"id"的字段对象    List<Method> list = this.matchPojoMethods(entity, "get");    Iterator<Method> iter = list.iterator();    while(iter.hasNext()) {      Method tempMethod = iter.next();      //如果方法名中带有ID字符串并且长度为2,则视为ID.      if(tempMethod.getName().lastIndexOf("Id") != -1 && tempMethod.getName().substring(3).length() == 2) {        //把ID字段的对象存放到一个变量中,然后在集合中删掉.        idMethod = tempMethod;        iter.remove();      //如果方法名去掉set/get字符串以后与pojo + "id"想符合(大小写不敏感),则视为ID      } else if((entity.getClass().getSimpleName() + "Id").equalsIgnoreCase(tempMethod.getName().substring(3))) {        idMethod = tempMethod;        iter.remove();              }    }        sql += idMethod.getName().substring(3).toLowerCase() + " = ?";        PreparedStatement statement = this.connection.prepareStatement(sql);        //为Id字段添加值    int i = 0;    if(idMethod.getReturnType().getSimpleName().indexOf("String") != -1) {      statement.setString(++i, this.getString(idMethod, entity));    } else {      statement.setInt(++i, this.getInt(idMethod, entity));    }            //执行    conn.execOther(statement);    //关闭连接    conn.closeConn();  }      /**   * 通过ID查询   */  public T findById(Object object) throws Exception{    String sql = "select * from " + persistentClass.getSimpleName().toLowerCase() + " where ";        //通过子类的构造函数,获得参数化类型的具体类型.比如BaseDAO<T>也就是获得T的具体类型    T entity = persistentClass.newInstance();        //存放Pojo(或被操作表)主键的方法对象    Method idMethod = null;        List<Method> list = this.matchPojoMethods(entity, "set");    Iterator<Method> iter = list.iterator();        //过滤取得Method对象    while(iter.hasNext()) {      Method tempMethod = iter.next();      if(tempMethod.getName().indexOf("Id") != -1 && tempMethod.getName().substring(3).length() == 2) {        idMethod = tempMethod;      } else if((entity.getClass().getSimpleName() + "Id").equalsIgnoreCase(tempMethod.getName().substring(3))){        idMethod = tempMethod;      }    }    //第一个字母转为小写    sql += idMethod.getName().substring(3,4).toLowerCase()+idMethod.getName().substring(4) + " = ?";        //封装语句完毕,打印sql语句    System.out.println(sql);        //获得连接    PreparedStatement statement = this.connection.prepareStatement(sql);        //判断id的类型    if(object instanceof Integer) {      statement.setInt(1, (Integer)object);    } else if(object instanceof String){      statement.setString(1, (String)object);    }        //执行sql,取得查询结果集.    ResultSet rs = conn.execQuery(statement);        //记数器,记录循环到第几个字段    int i = 0;            //把指针指向迭代器第一行    iter = list.iterator();        //封装    while(rs.next()) {      while(iter.hasNext()) {        Method method = iter.next();        if(method.getParameterTypes()[0].getSimpleName().indexOf("String") != -1) {          //由于list集合中,method对象取出的方法顺序与数据库字段顺序不一致(比如:list的第一个方法是setDate,而数据库按顺序取的是"123"值)          //所以数据库字段采用名字对应的方式取.          this.setString(method, entity, rs.getString(method.getName().substring(3).toLowerCase()));        } else if(method.getParameterTypes()[0].getSimpleName().indexOf("Date") != -1){          this.setDate(method, entity, rs.getDate(method.getName().substring(3).toLowerCase()));        } else if(method.getParameterTypes()[0].getSimpleName().indexOf("InputStream") != -1) {          this.setBlob(method, entity, rs.getBlob(method.getName().substring(3).toLowerCase()).getBinaryStream());        } else {          this.setInt(method, entity, rs.getInt(method.getName().substring(3).toLowerCase()));        }        }    }        //关闭结果集    rs.close();            //关闭预编译对象    statement.close();        return entity;  }      /**   * 过滤当前Pojo类所有带传入字符串的Method对象,返回List集合.   */  private List<Method> matchPojoMethods(T entity,String methodName) {    //获得当前Pojo所有方法对象    Method[] methods = entity.getClass().getDeclaredMethods();        //List容器存放所有带get字符串的Method对象    List<Method> list = new ArrayList<Method>();        //过滤当前Pojo类所有带get字符串的Method对象,存入List容器    for(int index = 0; index < methods.length; index++) {      if(methods[index].getName().indexOf(methodName) != -1) {        list.add(methods[index]);      }    }        return list;  }      /**   * 方法返回类型为int或Integer类型时,返回的SQL语句值.对应get   */  public Integer getInt(Method method, T entity) throws Exception{    return (Integer)method.invoke(entity, new Object[]{});  }    /**   * 方法返回类型为String时,返回的SQL语句拼装值.比如'abc',对应get   */  public String getString(Method method, T entity) throws Exception{    return (String)method.invoke(entity, new Object[]{});  }    /**   * 方法返回类型为Blob时,返回的SQL语句拼装值.对应get   */  public InputStream getBlob(Method method, T entity) throws Exception{    return (InputStream)method.invoke(entity, new Object[]{});  }      /**   * 方法返回类型为Date时,返回的SQL语句拼装值,对应get   */  public Date getDate(Method method, T entity) throws Exception{    return (Date)method.invoke(entity, new Object[]{});  }      /**   * 参数类型为Integer或int时,为entity字段设置参数,对应set   */  public Integer setInt(Method method, T entity, Integer arg) throws Exception{    return (Integer)method.invoke(entity, new Object[]{arg});  }    /**   * 参数类型为String时,为entity字段设置参数,对应set   */  public String setString(Method method, T entity, String arg) throws Exception{    return (String)method.invoke(entity, new Object[]{arg});  }    /**   * 参数类型为InputStream时,为entity字段设置参数,对应set   */  public InputStream setBlob(Method method, T entity, InputStream arg) throws Exception{    return (InputStream)method.invoke(entity, new Object[]{arg});  }      /**   * 参数类型为Date时,为entity字段设置参数,对应set   */  public Date setDate(Method method, T entity, Date arg) throws Exception{    return (Date)method.invoke(entity, new Object[]{arg});  }}

package com.employees.dao;import java.util.ArrayList;import java.util.List;import com.employees.po.Employees;public class EmployeesDao extends BaseDAO<Employees> {  // 添加员工信息的操作  public boolean addEmployees(final Employees employees) throws Exception {    save(employees);    return true;  }  // 将员工信息添加到表格中  public List<Employees> addEmployees(int id) throws Exception {    List<Employees> lstEmployees = new ArrayList<Employees>();    Employees employees = findById(id);    // 将当前封转好的数据装入对象中    lstEmployees.add(employees);    return lstEmployees;  }  public void deleteEmp(final Employees entity) throws Exception {    this.delete(entity);  }  public void updateEmp(final Employees entity) throws Exception {    this.update(entity);  }}

package com.employees.dao;import org.junit.Test;import com.employees.po.Employees;public class EmployeesDaoTest {  @Test  public void testAdd() throws Exception {    Employees emp = new Employees();    emp.setPname("tly");    emp.setPsex("男");    emp.setPbeliefs("xxxxx");    emp.setPaddr("天河");    emp.setPhobby("打篮球");    emp.setPsubject("计算机");    emp.setPtel("123456");    EmployeesDao dao = new EmployeesDao();    dao.addEmployees(emp);  }  @Test  public void testUpdate() throws Exception {    EmployeesDao dao = new EmployeesDao();    Employees emp = dao.findById(14);    emp.setPtel("999999");    dao.updateEmp(emp);  }  @Test  public void testdelete() throws Exception {    EmployeesDao dao = new EmployeesDao();    Employees emp = dao.findById(15);    dao.deleteEmp(emp);  }}