JDBC_ORM原理JAVA277-279

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一、S03E277_01JDBC_ORM原理、使用Object数组存储一条记录

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引用表emp
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#右击该properties文件--properties--Resource--Text file encoding，选中other,选择其它编码方式。#如UTF-8或GBK,这样就能在properties里面输入中文，而不会自动转成Unicode了。#java中的properties文件是一种配置文件，主要用于表达配置信息。#文件类型为*.properties，格式为文本文件，文件内容是"键=值"的格式。#在properties文件中，可以用"#"来作注释#MySQL连接配置mysqlDriver=com.mysql.jdbc.DrivermysqlURL=jdbc:mysql://localhost:3306/sormmysqlUser=rootmysqlPwd=mysql#Oracle连接配置#...

package com.test.orm;import java.io.IOException;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import java.util.Properties;public class JDBCUtil {    static Properties pros = null;  //可以帮助读取和处理资源文件中的信息    static {    //加载JDBCUtil类的时候调用        pros = new Properties();        try {            pros.load(Thread.currentThread().getContextClassLoader().getResourceAsStream("db.properties"));        } catch (IOException e) {            e.printStackTrace();        }    }    public static Connection getMysqlConn(){        try {            Class.forName(pros.getProperty("mysqlDriver"));            return DriverManager.getConnection(pros.getProperty("mysqlURL"),                    pros.getProperty("mysqlUser"),pros.getProperty("mysqlPwd"));        } catch (Exception e) {            e.printStackTrace();            return null;        }    }    //可以重载多个，这里就懒得写了    public static void close(ResultSet rs,Statement st,Connection conn){        try {            if (rs!=null) {                rs.close();            }        } catch (SQLException e) {            e.printStackTrace();        }        try {            if (st!=null) {                st.close();            }        } catch (SQLException e) {            e.printStackTrace();        }        try {            if (conn!=null) {                conn.close();            }        } catch (SQLException e) {            e.printStackTrace();        }    }}

package com.test.orm;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.util.ArrayList;import java.util.List;/** * 使用Object[]来封装一条记录 * 使用List<Object[]>存储多条记录 */public class Demo01 {    public static void main(String[] args) {        Connection conn = JDBCUtil.getMysqlConn();        PreparedStatement ps = null;        ResultSet rs = null;        List <Object[]> objsList = new ArrayList<Object[]>();        try {            ps = conn.prepareStatement("select empname,salary,age from emp where id > ?");            ps.setObject(1, 1); //从1开始算参数            rs = ps.executeQuery();            while (rs.next()) {                Object[] objs = new Object[3];  //一个Object数组封装了一条记录的信息！                objs[0] = rs.getString(1);                objs[1] = rs.getDouble(2);                objs[2] = rs.getInt(3);                objsList.add(objs);            }        } catch (SQLException e) {            e.printStackTrace();        } finally {            JDBCUtil.close(rs, ps, conn);        }        for (Object[] objs : objsList) {            System.out.println(objs[0]+"--"+objs[1]+"--"+objs[2]);        }    }}

二、S03E278_01JDBC_ORM原理、Map封装一条记录、Map和List封装多条记录

package com.test.orm;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;/** * 使用Map存储一条记录中的多行 * 使用List<Map>存储各行中的多行 * 使用Map<Map>存储各行中的多行 */public class Demo02 {    /**     * 使用Map存储一条记录中的多行     */    public static void test01(){        Connection conn = JDBCUtil.getMysqlConn();        PreparedStatement ps = null;        ResultSet rs = null;        Map<String,Object> row = new HashMap<String,Object>();  //使用一个Map封装一条记录        try {            ps = conn.prepareStatement("select empname,salary,age from emp where id = ?");            ps.setObject(1, 1); //从1开始算参数            rs = ps.executeQuery();            while (rs.next()) {                row.put("empname", rs.getObject(1));                row.put("salary", rs.getObject(2));                row.put("age", rs.getObject(3));            }        } catch (SQLException e) {            e.printStackTrace();        } finally {            JDBCUtil.close(rs, ps, conn);        }        System.out.println("Map存储单行的多列：");        //遍历Map，就是遍历这一行的多列的信息        for (String key : row.keySet()) {            System.out.print(key+"--"+row.get(key)+"\t");        }        System.out.println();    }    /**     * 使用List<Map>存储各行中的多行     */    public static void test02(){        Connection conn = JDBCUtil.getMysqlConn();        PreparedStatement ps = null;        ResultSet rs = null;        //List封装        List<Map<String,Object>> list = new ArrayList<Map<String,Object>>();        try {            ps = conn.prepareStatement("select empname,salary,age from emp where id > ? order by empname");            ps.setObject(1, 1); //从1开始算参数            rs = ps.executeQuery();            while (rs.next()) {                Map<String,Object> row = new HashMap<String,Object>();  //使用一个Map封装一条记录                row.put("empname", rs.getObject(1));                row.put("salary", rs.getObject(2));                row.put("age", rs.getObject(3));                list.add(row);  //Map加入List            }        } catch (SQLException e) {            e.printStackTrace();        } finally {            JDBCUtil.close(rs, ps, conn);        }        System.out.println("List存储各行的多列：");        //遍历list        for (Map<String, Object> map : list) {            //遍历Map，就是遍历这一行的多列的信息            for (String key : map.keySet()) {                System.out.print(key+"--"+map.get(key)+"\t");            }            System.out.println();        }    }    /**     * 使用Map<Map>存储各行中的多行     */    public static void test03(){        Connection conn = JDBCUtil.getMysqlConn();        PreparedStatement ps = null;        ResultSet rs = null;        //Map封装        Map<String,Map<String,Object>> maps = new HashMap<String,Map<String,Object>>();        try {            ps = conn.prepareStatement("select empname,salary,age from emp where id > ? order by empname");            ps.setObject(1, 1); //从1开始算参数            rs = ps.executeQuery();            while (rs.next()) {                Map<String,Object> row = new HashMap<String,Object>();  //使用一个Map封装一条记录                row.put("empname", rs.getObject(1));                row.put("salary", rs.getObject(2));                row.put("age", rs.getObject(3));                maps.put(rs.getString(1), row); //Map加入Map            }        } catch (SQLException e) {            e.printStackTrace();        } finally {            JDBCUtil.close(rs, ps, conn);        }        System.out.println("Map存储各行的多列：");        //遍历Map        for (String empname : maps.keySet()) {            Map<String,Object> row = maps.get(empname);            //遍历Map，就是遍历这一行的多列的信息            for (String key : row.keySet()) {                System.out.print(key+"--"+row.get(key)+"\t");            }            System.out.println();        }    }    public static void main(String[] args) {        test01();   //单条        test02();   //多行        test03();   //多行    }}

三、S03E279_01JDBC_ORM原理、使用javabean对象封装一条记录

package com.test.orm;import java.sql.Date;public class Emp {  //表结构和类对应    private Integer id; //尽量用包装类    private String empname;    private Double salary;    private Date birthday;    private Integer age;    private Integer depId;    public Emp() {    }    public Emp(String empname, Double salary, Integer age) {        super();        this.empname = empname;        this.salary = salary;        this.age = age;    }    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getEmpname() {        return empname;    }    public void setEmpname(String empname) {        this.empname = empname;    }    public Double getSalary() {        return salary;    }    public void setSalary(Double salary) {        this.salary = salary;    }    public Date getBirthday() {        return birthday;    }    public void setBirthday(Date birthday) {        this.birthday = birthday;    }    public Integer getAge() {        return age;    }    public void setAge(Integer age) {        this.age = age;    }    public Integer getDepId() {        return depId;    }    public void setDepId(Integer depId) {        this.depId = depId;    }}

package com.test.orm;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.util.ArrayList;import java.util.List;/** * 使用Javabean对象存储一条记录中的多行 * 使用List<Javabean>存储各行中的多行 */public class Demo03 {    /**     * 使用Javabean对象存储一条记录中的多行     */    public static void test01(){        Connection conn = JDBCUtil.getMysqlConn();        PreparedStatement ps = null;        ResultSet rs = null;        Emp emp = null;        try {            ps = conn.prepareStatement("select empname,salary,age from emp where id = ?");            ps.setObject(1, 1); //从1开始算参数            rs = ps.executeQuery();            while (rs.next()) {                emp = new Emp(rs.getString(1), rs.getDouble(2), rs.getInt(3));                System.out.println("Javabean对象存储一条记录中的多行");                System.out.println(emp.getEmpname()+"--"+emp.getSalary()+"--"+emp.getAge());            }        } catch (SQLException e) {            e.printStackTrace();        } finally {            JDBCUtil.close(rs, ps, conn);        }    }    /**     * 使用List<Javabean>存储各行中的多行     */    public static void test02(){        Connection conn = JDBCUtil.getMysqlConn();        PreparedStatement ps = null;        ResultSet rs = null;        //List封装        List<Emp> list = new ArrayList<Emp>();        try {            ps = conn.prepareStatement("select empname,salary,age from emp where id > ? order by empname");            ps.setObject(1, 1); //从1开始算参数            rs = ps.executeQuery();            while (rs.next()) {                Emp emp = new Emp(rs.getString(1), rs.getDouble(2), rs.getInt(3));                 list.add(emp);            }        } catch (SQLException e) {            e.printStackTrace();        } finally {            JDBCUtil.close(rs, ps, conn);        }        System.out.println("List存储各行的多列：");        //遍历list        for (Emp emp : list) {            System.out.println(emp.getEmpname()+"--"+emp.getSalary()+"--"+emp.getAge());        }    }    public static void main(String[] args) {        test01();   //单条        test02();   //多行    }}

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