db.properties配置文件
代码如下
db.driver=com.mysql.cj.jdbc.Driver
db.url=jdbc:mysql://localhost:3306/db?serverTimezone=PRC&useSSL=false&useUnicode=true&characterEncoding=utf8
db.username=root
db.password=
package com;
import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.*;
public class Newdbutil {
private String driver;
private String url;
private String username;
private String password;
private String dbname;
private Connection conn;
private int recordcount; //总记录条数
private int currpage = 1;//当前页
private int pagesize = 10;//每页记录条数
private int pagecount = 1;//总页数
/**
* 初始化方法，完成配置文件的读取（driver，URL，username，password）
*/
public void init() {
Properties prop = new Properties();
InputStream is =this.getclass().getClassLoader().getResourceAsStream("db.properties");
try {
prop.load(is);
this.driver = prop.getProperty("db.driver");
this.url = prop.getProperty("db.url");
this.username = prop.getProperty("db.username");
this.password = prop.getProperty("db.password");
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 无参构造方法链接数据库中的test库
*/
public Newdbutil() {
this.init();
try {
Class.forName(this.driver);
try {
this.conn = DriverManager.getConnection(this.url, this.username, this.password);
} catch (SQLException e) {
e.printStackTrace();
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
/**
* <p>功能：实现数据插入操作</p>
*
* @param sql 数据库预处理语句，实现插入数据功能
* @param objs 根据预处理语句填写对应内容，有多少个问号就填几个
* @return
*/
public int save(String sql, Object... objs) {
int result = 0;
try {
PreparedStatement pst = this.conn.prepareStatement(sql);
for (int i = 0; i < objs.length; i++) {
pst.setObject(i + 1, objs[i]);
}
result = pst.executeUpdate();
pst.close();
} catch (SQLException e) {
e.printStackTrace();
}
return result;
}
/**
* <p>功能：实现数据插入操作</p>
*
* @param sql 数据库预处理语句，实现插入数据功能
* @param values 根据预处理语句填写对应内容，有多少个问号数组中就填几个值
* @return
*/
public int add(String sql, Object[] values) {
int result = 0;
try {
PreparedStatement pst = this.conn.prepareStatement(sql);
int indes = 1;
for (Object obj : values) {
pst.setObject(indes++, obj);
}
result = pst.executeUpdate();
pst.close();
} catch (SQLException e) {
e.printStackTrace();
}
return result;
}
/**
* @param tablename 表名
* @param values map集合，key为表的列名，values为添加的值。
* @return
*/
public int insert(String tablename, Map<String, Object> values) {
int result = 0;
StringBuilder f = new StringBuilder(values.size());
StringBuilder v = new StringBuilder(values.size());
Set<String> kset = values.keySet();
for (String key : kset) {
f.append(key + ",");
v.append("?,");
}
String sql = String.format("insert into %s(%s) values(%s)", tablename, f.substring(0, f.length() - 1), v.substring(0, v.length() - 1));
try {
PreparedStatement pst = this.conn.prepareStatement(sql);
int index = 1;
for (String key : kset) {
pst.setObject(index++, values.get(key));
}
result = pst.executeUpdate();
pst.close();
} catch (SQLException e) {
e.printStackTrace();
}
return result;
}
/**
* 功能：返回一个表的主键名
*
* @param tablename
* @return
*/
public String getPk(String tablename) {
String pk = null;
DatabaseMetaData dbmd;
try {
dbmd = this.conn.getMetaData();
ResultSet rs = dbmd.getPrimaryKeys(this.dbname, null, tablename);
if (rs.next()) {
pk = rs.getString(4);
}
} catch (SQLException e) {
e.printStackTrace();
}
return pk;
}
/**
* 功能：根据主键删除一条记录
*
* @param tablename 表名
* @param primarykey 要删除记录的主键名
* @return
*/
public int delete(String tablename, Object primarykey) {
int result = 0;
String sql = String.format("delete from %s where %s = ?", tablename, getPk(tablename));
try {
PreparedStatement pst = this.conn.prepareStatement(sql);
pst.setObject(1, primarykey);
result = pst.executeUpdate();
pst.close();
} catch (SQLException e) {
e.printStackTrace();
}
return result;
}
/**
* @param tablename
* @param where 表示删除条件一个条件一个问号
* @param objs 根据预处理语句填写对应内容，有多少个问号就填几个
* @return
*/
public int delete(String tablename, String where, Object... objs) {
int result = 0;
String sql = String.format("delete from %s %s", tablename, where);
try {
PreparedStatement pst = this.conn.prepareStatement(sql);
for (int i = 0; i < objs.length; i++) {
pst.setObject(i + 1, objs[i]);
}
result = pst.executeUpdate();
pst.close();
} catch (SQLException e) {
e.printStackTrace();
}
return result;
}
/**
* @param sql update tablename set name = ? ... where id = ?,
* @param objs "andy",...,100 根据update语句填写共有几个值
* @return
*/
public int update(String sql, Object... objs) {
int result = 0;
try {
PreparedStatement pst = this.conn.prepareStatement(sql);
for (int i = 0; i < objs.length; i++) {
pst.setObject(i + 1, objs[i]);
}
} catch (SQLException e) {
e.printStackTrace();
}
return result;
}
/**
* @param tablename 表名
* @param m map集合存放要修改的列名及值
* @param where 修改的条件
* @return
*/
public int update(String tablename, Map<String, Object> m, String where) {
int result = 0;
StringBuilder s = new StringBuilder();
for (String k : m.keySet()) {
s.append(k + "=?,");
}
String sql = String.format("update %s set %s %s", tablename, s.toString().substring(0, s.length() - 1), where);
try {
PreparedStatement pst = this.conn.prepareStatement(sql);
int i = 0;
for (Object o : m.values()) {
pst.setObject(++i, o);
}
result = pst.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
return result;
}
/**
* 功能实现修改数据
*
* @param tablename 表名
* @param map map集合存放要修改的列名及值，和表的主键名和主键值
* @return
*/
public int update(String tablename, Map<String, Object> map) {
int result = 0;
String pk = getPk(tablename);
if (map.containsKey(pk)) {
StringBuilder f = new StringBuilder(map.size());
Object pkname = map.get(pk);
map.remove(pk);
Set<String> kset = map.keySet();
for (String key : kset) {
f.append(key + "=?,");
}
String sql = String.format("update %s set %s where %s=?", tablename, f.substring(0, f.length() - 1), pk);
try {
PreparedStatement pst = this.conn.prepareStatement(sql);
int index = 1;
for (String key : kset) {
pst.setObject(index++, map.get(key));
}
pst.setObject(index, pkname);
result = pst.executeUpdate();
pst.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
return result;
}
/**
* 功能：实现表的查询工作 只能查询一条结果
*
* @param sql sql查询语句// select score name from stu where id = ?,1
* @param params 条件
* @return
*/
public Map<String, Object> queryone(String sql, Object... params) {
Map<String, Object> map = null;
try {
PreparedStatement pst = this.conn.prepareStatement(sql);
for (int i = 0; i < params.length; i++) {
pst.setObject(i + 1, params[i]);
}
ResultSet rs = pst.executeQuery();
ResultSetMetaData rsmd = rs.getMetaData();
String[] keys = new String[rsmd.getColumnCount()];
for (int c = 1; c <= rsmd.getColumnCount(); c++) {
keys[c - 1] = rsmd.getColumnLabel(c);
}
map = new HashMap<String, Object>();
rs.next();
for (int n = 0; n < keys.length; n++) {
map.put(keys[n], rs.getObject(keys[n]));
}
} catch (SQLException e) {
e.printStackTrace();
}
return map;
}
/**
* 功能：实现表的查询工作 能查询多条结果,返回List<Map<String,Object>>集合。一条结果就是一个map。
*
* @param sql sql查询语句// select score name from stu where id = ?,1
* @param objs 条件
* @return
*/
public List<Map<String, Object>> query(String sql, Object... objs) {
List<Map<String, Object>> list = null;
try {
PreparedStatement pst = this.conn.prepareStatement(sql);
for (int i = 0; i < objs.length; i++) {
pst.setObject(i + 1, objs[i]);
}
ResultSet rs = pst.executeQuery();
ResultSetMetaData rsmd = rs.getMetaData();
String[] keys = new String[rsmd.getColumnCount()];
for (int m = 1; m <= rsmd.getColumnCount(); m++) {
keys[m - 1] = rsmd.getColumnLabel(m);
}
list = new ArrayList<Map<String, Object>>();
while (rs.next()) {
Map<String, Object> map = new HashMap<String, Object>();
for (int n = 0; n < keys.length; n++) {
map.put(keys[n], rs.getObject(keys[n]));
}
list.add(map);
}
} catch (SQLException e) {
e.printStackTrace();
}
return list;
}
/** 实现分页查询与多条查询类似
* @param sql select * from stu where id>?,1
* @param objs 条件
* @return
*/
public List<Map<String, Object>> page(String sql, Object... objs) {
List<Map<String, Object>> list = null;
String ccc = "select count(*)" + sql.substring(sql.indexOf("from"));
try {
PreparedStatement pst = this.conn.prepareStatement(ccc);
int index = 1;
for (Object o : objs) {
pst.setObject(index++, o);
}
ResultSet rs = pst.executeQuery();
rs.next();
this.recordcount = rs.getInt(1);//总记录条数
this.pagecount = this.recordcount % this.pagesize == 0 ? this.recordcount / this.pagesize : this.recordcount / this.pagesize + 1;
if (this.currpage < 1) this.currpage = 1;
if (this.currpage > getPagecount()) this.currpage = this.pagecount;
String psql = sql + " limit ?,?";
pst = this.conn.prepareStatement(psql);
index = 1;
for (Object o : objs) {
pst.setObject(index++, o);
}
pst.setInt(index++, this.currpage * this.pagesize - this.pagesize);
pst.setInt(index, this.pagesize);
rs = pst.executeQuery();
ResultSetMetaData rsmd = rs.getMetaData();
list = new ArrayList<Map<String, Object>>();
while (rs.next()) {
Map<String, Object> m = new HashMap<String, Object>();
int cc = rsmd.getColumnCount();
for (int i = 1; i <= cc; i++) {
String name = rsmd.getColumnLabel(i);
m.put(name, rs.getObject(name));
}
list.add(m);
}
} catch (SQLException e) {
e.printStackTrace();
}
return list;
}
/**
* 实现分页查询功能
* @param currpage 当前页（查询的第几页）
* @param pagesize 每页的记录条数
* @param tablename 表名
* @param fields 查询的对象（列名）
* @param where 查询的条件
* @return
*/
public List<Map<String, Object>> page(int currpage, int pagesize, String tablename, String fields, String where) {
this.currpage = currpage;
this.pagesize = pagesize;
String sql = String.format("select %s from %s %s", fields, tablename, where);
return page(sql);
}
public int getRecordcount() {
return recordcount;
}
public void setRecordcount(int recordcount) {
this.recordcount = recordcount;
}
public int getCurrpage() {
return currpage;
}
public void setCurrpage(int currpage) {
this.currpage = currpage;
}
public int getPagesize() {
return pagesize;
}
public void setPagesize(int pagesize) {
this.pagesize = pagesize;
}
public int getPagecount() {
return pagecount;
}
public void setPagecount(int pagecount) {
this.pagecount = pagecount;
}
public String getDriver() {
return driver;
}
public void setDriver(String driver) {
this.driver = driver;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getDbname() {
return dbname;
}
public void setDbname(String dbname) {
this.dbname = dbname;
}
public Connection getConn() {
return conn;
}
public void setConn(Connection conn) {
this.conn = conn;
}
}