Java EE 查询 将数据库中对应的表逐行转换成DAO实体类。

4/14/2017 3:20:05 PM

Java EE 查询 将数据库中对应的表逐行转换成DAO实体类。List方式返回。自动赋值时忽略大小写的名称进行匹配，自动赋值到指定的实体类中。

需要导入mysql-connector-java-xxxx-bin.jar包

直接上代码:

package com.hbbc.test;import java.io.IOException;import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.ResultSetMetaData;import java.sql.SQLException;import java.sql.Statement;import java.util.ArrayList;import java.util.Date;import java.util.List;import java.util.Properties;public class DBUtil {public Connection openConnection(String propertiesName){    try {        Class.forName("com.mysql.jdbc.Driver");        Properties prop=new Properties();        prop.load(DBUtil.class.getClassLoader().getResourceAsStream(propertiesName!=""?propertiesName:"main.properties"));        String url=prop.getProperty("url");        String username=prop.getProperty("username");        String password=prop.getProperty("password");        return DriverManager.getConnection(url, username, password);    } catch (ClassNotFoundException | IOException | SQLException e) {        e.printStackTrace();    }    return null;}@SuppressWarnings("unchecked")public static void main(String[] args) {    String sql="SELECT * FROM testdb";    ArrayList<UserBean> beanList=(ArrayList<UserBean>) DBUtil.QueryDB(sql, UserBean.class);    for (int i = 0; i < beanList.size(); i++) {        System.out.println("id:"+beanList.get(i).getId()+",age:"+beanList.get(i).getAge()+",username:"+beanList.get(i).getUserName()+",sex:"+beanList.get(i).isSex()+",addTime:"+beanList.get(i).getAddTime());    }}/** *  * @param sql 查询语句 * @param clazz 实体类型 * @return  返回的list类型，需强制转换 */public static List<?> QueryDB(String sql,Class<?> clazz){    DBUtil dbu=new DBUtil();    Connection conn=dbu.openConnection("");    ArrayList<Object> resultlist=new ArrayList<>();    try {            java.sql.PreparedStatement pst=conn.prepareStatement(sql);            Statement stmt=conn.createStatement();            ResultSet rs=stmt.executeQuery(sql);             ResultSetMetaData rsd=pst.executeQuery().getMetaData();            pst=conn.prepareStatement(sql);            //获取反射对象中的属性集合            Field[] field=clazz.getDeclaredFields();            while (rs.next()) {                Object obj=clazz.newInstance();//反射对对象实例化                //数据表中列数,获取列名称下标从第1个开始遍历                for (int k = 1; k <= rsd.getColumnCount(); k++) {                    //当前类中属性的数量                for (int j = 0; j < field.length; j++) {                        //获取数据表中当前列明                        String columnName=rsd.getColumnName(k);                        //如果当前数据表列中的名称和类中属性名称相同，就执行属性赋值方法                        if (columnName.equalsIgnoreCase(field[j].getName())) {                            //System.out.println("field.length:"+field.length);                            //属性的类型                            String typeName=field[j].getGenericType().toString();                            //以下是常用的类型                            if (("class java.lang.String").equals(typeName)) {                                //属性赋值                                Method m=clazz.getMethod("set"+columnName, String.class);                                m.invoke(obj,rs.getString(columnName));                            }else if (("int").equals(typeName)) {                                Method m=clazz.getMethod("set"+columnName, int.class);                                m.invoke(obj,rs.getInt(columnName));                            }else if(("boolean").equals(typeName)){                                Method m=clazz.getMethod("set"+columnName, boolean.class);                                m.invoke(obj,rs.getBoolean(columnName));                            }else if ("class java.util.Date".equals(typeName)) {                                Method m=clazz.getMethod("set"+columnName, Date.class);                                m.invoke(obj,rs.getDate(columnName));                            }//                              System.out.print("typeName:"+typeName+",Name:"+field[j].getName()+",ColumnName:"+columnName);//                              System.out.println("---------------执行完");                        }                    }                }                resultlist.add(obj);            }            return resultlist;    } catch (SQLException e) {        System.out.println("数据库连接失败");        e.printStackTrace();    } catch (NoSuchMethodException e) {        System.out.println("没有这个方法");        e.printStackTrace();    } catch (SecurityException e) {        e.printStackTrace();    } catch (IllegalAccessException e) {        System.out.println("获取不到数据表中当前的值");        e.printStackTrace();    } catch (IllegalArgumentException e) {        System.out.println("反射，传递参数错误");        e.printStackTrace();    } catch (InvocationTargetException e) {        e.printStackTrace();    } catch (InstantiationException e) {        System.out.println("无法对该类newInstance");        e.printStackTrace();    }    return null;}}

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如下是实体类:

package com.hbbc.test;import java.util.Date;public class UserBean {private String userName;private int id;private int age;private boolean sex;private Date addTime;public String getUserName() {    return userName;}public void setUserName(String userName) {    this.userName = userName;}public int getId() {    return id;}public void setId(int id) {    this.id = id;}public int getAge() {    return age;}public void setAge(int age) {    this.age = age;}public boolean isSex() {    return sex;}public void setSex(boolean sex) {    this.sex = sex;}public Date getAddTime() {    return addTime;}public void setAddTime(Date addTime) {    this.addTime = addTime;}}

Demo查看：

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