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;
}
}
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：
Demo下载
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