泛型dao+mysql数据库+增删改查

1.泛型dao接口

package dao;/** *  * @author Kevin * */public interface GenericityDao<T> {}

2.创建Javabean

package javabean;import dao.GenericityDao;/** *  * @author Kevin * */public class Users implements GenericityDao<Users> {       // 用户id        private Integer id;                // 用户名               private String name;        // 密码       private String password;        // 年龄       private Integer age;        // 无参构造方法public Users() {}        // 有参构造方法public Users(int id, String name, String password, int age) {this.id = id;this.name = name;this.password = password;this.age = age;}        // 成员变量的get、set方法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 getPassword() {return password;}public void setPassword(String password) {this.password = password;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}}

3.连接mysql数据库的util类

package util;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;/** *  * @author Kevin * */public class DBConnection {public static Connection getConnection() {Connection conn = null;String url = "jdbc:mysql://localhost:3306/student";String username = "root";String password = "root";try {                        // 加载驱动                       Class.forName("com.mysql.jdbc.Driver");                        // 获取数据库连接                       conn = DriverManager.getConnection(url, username, password);} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}return conn;}}

4.dao的具体类

package dao;import java.beans.IntrospectionException;import java.beans.PropertyDescriptor;import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import java.util.ArrayList;import java.util.List;import util.DBConnection;/** *  * @author Kevin * */public class Dao {// 获取表名public <T> String getTableName(Class<? extends GenericityDao<T>> clazz) {// 获取 包名.类名String className = clazz.getName();// 获取 表名String tableName = className.substring(className.lastIndexOf(".") + 1,className.length());return tableName;}// 获得一个有属性值的实体类public <T> GenericityDao<T> getJavaBean(Class<? extends GenericityDao<T>> clazz, ResultSet rs)throws IntrospectionException, IllegalArgumentException,IllegalAccessException, InvocationTargetException, SQLException,InstantiationException {GenericityDao<T> g = clazz.newInstance();                // 获取所有的成员变量               Field[] field = clazz.getDeclaredFields();int i = 1;for (Field f : field) {PropertyDescriptor pd = new PropertyDescriptor(f.getName(), clazz);Method setMethod = pd.getWriteMethod();                        // 判断方法的返回值类型                       if (f.getType() == String.class) {setMethod.invoke(g, rs.getString(i));i++;} else if (f.getType() == Integer.class) {setMethod.invoke(g, rs.getInt(i));i++;}}return g;}// 增加insert@SuppressWarnings("unchecked")public <T> void insertInfo(GenericityDao<T> gd) {// 获取 class 包名.类名Class<? extends GenericityDao<T>> clazz = (Class<? extends GenericityDao<T>>) gd.getClass();String tableName = getTableName(clazz);String sql = "insert into " + tableName + "(";Field[] fields = clazz.getDeclaredFields();for (Field field : fields) {String fieldName = field.getName();sql = sql + fieldName + ",";}// 去除最后sql语句最后的逗号sql = sql.substring(0, sql.length() - 1);sql += ") values (";// 获取属性的数量总数int fieldLength = fields.length;for (int i = 1; i <= fieldLength; i++) {sql += "?,";}sql = sql.substring(0, sql.length() - 1);sql += ");";Connection conn = null;PreparedStatement ps = null;try {conn = DBConnection.getConnection();ps = conn.prepareStatement(sql);int i = 0;// 获取属性(带路径)Field[] field = clazz.getDeclaredFields();Field.setAccessible(field, true);// 遍历属性for (Field field1 : field) {// i用来匹配多少个'？'i += 1;PropertyDescriptor pd = new PropertyDescriptor(field1.getName(), clazz);Method getMethod = pd.getReadMethod();Object obj = (Object) getMethod.invoke(gd);// 判断属性的类型if (field1.getType() == String.class) {ps.setString(i, obj.toString());} else if (field1.getType() == Integer.class) {ps.setInt(i, Integer.parseInt(obj.toString()));}}System.out.println(sql);ps.execute();} catch (SQLException e) {e.printStackTrace();} catch (IntrospectionException e) {e.printStackTrace();} catch (IllegalArgumentException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();} finally {if (ps != null) {try {ps.close();} catch (SQLException e) {e.printStackTrace();}}if (conn != null) {try {conn.close();} catch (SQLException e) {e.printStackTrace();}}}}// 删除delete@SuppressWarnings("unchecked")public <T> void deleteInfo(GenericityDao<T> gd) {Class<? extends GenericityDao<T>> clazz = (Class<? extends GenericityDao<T>>) gd.getClass();String tableName = getTableName(clazz);String sql = "delete from " + tableName + " where ";Connection conn = null;Statement st = null;try {conn = DBConnection.getConnection();st = conn.createStatement();Field[] field = clazz.getDeclaredFields();Field.setAccessible(field, true);for (Field field1 : field) {PropertyDescriptor pd = new PropertyDescriptor(field1.getName(), clazz);Method getMethod = pd.getReadMethod();Object obj = (Object) getMethod.invoke(gd);if (field1.getType() == String.class) {sql += field1.getName() + "='" + obj.toString() + "' and ";} else if (field1.getType() == Integer.class) {sql += field1.getName() + "='"+ Integer.parseInt(obj.toString()) + "' and ";}}sql = sql.substring(0, sql.length() - 5) + ";";System.out.println(sql);st.execute(sql);} catch (SQLException e) {e.printStackTrace();} catch (IntrospectionException e) {e.printStackTrace();} catch (IllegalArgumentException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();} finally {if (st != null) {try {st.close();} catch (SQLException e) {e.printStackTrace();}}if (conn != null) {try {conn.close();} catch (SQLException e) {e.printStackTrace();}}}}// 修改update@SuppressWarnings("unchecked")public <T> void updateInfo(GenericityDao<T> gd, GenericityDao<T> gd1) {Class<? extends GenericityDao<T>> clazz = (Class<? extends GenericityDao<T>>) gd.getClass();Class<? extends GenericityDao<T>> clazz1 = (Class<? extends GenericityDao<T>>) gd1.getClass();String tableName = getTableName(clazz);String sql = "update " + tableName + " set ";Connection conn = null;Statement st = null;try {conn = DBConnection.getConnection();st = conn.createStatement();Field[] field1 = clazz.getDeclaredFields();Field.setAccessible(field1, true);for (Field f : field1) {PropertyDescriptor pd = new PropertyDescriptor(f.getName(),clazz1);Method getMethod = pd.getReadMethod();Object obj = (Object) getMethod.invoke(gd1);if (f.getType() == String.class) {sql += f.getName() + "='" + obj.toString() + "',";} else if (f.getType() == Integer.class) {sql += f.getName() + "='"+ Integer.parseInt(obj.toString()) + "',";}}sql = sql.substring(0, sql.length() - 1) + " where ";Field[] field = clazz1.getDeclaredFields();Field.setAccessible(field, true);for (Field f : field) {PropertyDescriptor pd = new PropertyDescriptor(f.getName(),clazz);Method getMethod = pd.getReadMethod();Object obj = (Object) getMethod.invoke(gd);if (f.getType() == String.class) {sql += f.getName() + "='" + obj.toString() + "' and ";} else if (f.getType() == Integer.class) {sql += f.getName() + "='"+ Integer.parseInt(obj.toString()) + "' and ";}}sql = sql.substring(0, sql.length() - 5) + ";";System.out.println(sql);st.execute(sql);} catch (SQLException e) {e.printStackTrace();} catch (IntrospectionException e) {e.printStackTrace();} catch (IllegalArgumentException e) {e.printStackTrace();} catch (IllegalAccessException e) { e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();} finally {if (st != null) {try {st.close();} catch (SQLException e) {e.printStackTrace();}}if (conn != null) {try {conn.close();} catch (SQLException e) {e.printStackTrace();}}}}// 查询所有@SuppressWarnings("unchecked")public <T> List<GenericityDao<T>> selectAll(GenericityDao<T> gd) {Class<? extends GenericityDao<T>> clazz = (Class<? extends GenericityDao<T>>) gd.getClass();List<GenericityDao<T>> list = new ArrayList<GenericityDao<T>>();String tableName = getTableName(clazz);String sql = "select * from " + tableName + ";";Connection conn = null;Statement st = null;ResultSet rs = null;try {conn = DBConnection.getConnection();st = conn.createStatement();rs = st.executeQuery(sql);while (rs.next()) {GenericityDao<T> g = getJavaBean(clazz, rs);list.add(g);}} catch (SQLException e) {e.printStackTrace();} catch (InstantiationException e) {e.printStackTrace();} catch (IllegalAccessException e) { e.printStackTrace();} catch (IntrospectionException e) {e.printStackTrace();} catch (IllegalArgumentException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();} finally {if (rs != null) {try {rs.close();} catch (SQLException e) {e.printStackTrace();}}if (st != null) {try {st.close();} catch (SQLException e) {e.printStackTrace();}}if (conn != null) {try {conn.close();} catch (SQLException e) {e.printStackTrace();}}}return list;}}