Java MySql database read and write auxiliary class

 Java encapsulates the auxiliary class used to access the MySQL database, using the MySQL JDBC driver.

package src.framework.db;

import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import javax.sql.RowSet;
import javax.sql.rowset.CachedRowSet;
import javax.sql.rowset.RowSetFactory;
import javax.sql.rowset.RowSetProvider;

import org.json.JSONException;
import org.json.JSONObject;

public class MySQLHelper {

    private String _connection;
    private String _userName;
    private String _password;

    public MySQLHelper(final String connection, final String userName, final String password) {
        _connection = connection;
        _userName = userName;
        _password = password;
    }

    /**
     * 取得数据库连接
     */
    private Connection getConnection() {
        try {
            // Class.forName("com.mysql.jdbc.Driver");
            Class.forName("com.mysql.cj.jdbc.Driver"); // 数据库版本在6.0以上，原来（com.mysql.jdbc.Driver）已经被废弃了，要进行更换驱动:com.mysql.cj.jdbc.Driver
            final java.sql.Connection conn = DriverManager.getConnection(_connection, _userName, _password);
            return conn;
        } catch (final Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 关闭数据库连接
     */
    private void close(final Connection conn, final PreparedStatement pstm, final ResultSet rs) {
        try {
            if (conn != null) {
                conn.close();
            }
            if (pstm != null) {
                pstm.close();
            }
            if (rs != null) {
                rs.close();
            }
        } catch (final Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }

    /**
     * 执行单个数据库操作 Insert,Update,Delete
     * 
     * @return 成功执行的记录数
     */
    public Integer Update(final String sql, final String[] params) {
        Connection conn = null;
        PreparedStatement pstm = null;

        try {
            conn = getConnection();
            pstm = conn.prepareStatement(sql);
            if (params != null) {
                for (int i = 0; i < params.length; i++) {
                    pstm.setString(i + 1, params[i]);
                }
            }
            return pstm.executeUpdate();

        } catch (final Exception e) {
            e.printStackTrace();
            return -1;
        } finally {
            close(conn, pstm, null);
        }
    }

    /**
     * 执行多个数据库操作，包含事务处理功能
     * 
     * @return 如果事务执行成功返回1，如果事务执行不成功返回0
     */
    public Integer Update(final String[] sqls, final String[][] params) {
        Connection conn = null;
        PreparedStatement pstm = null;
        try {
            conn = getConnection();
            // 禁止自动提交事务
            conn.setAutoCommit(false);
            for (int i = 0; i < sqls.length; i++) {
                pstm = conn.prepareStatement(sqls[i]);
                if (params != null) {
                    for (int j = 0; j < params[i].length; j++) {
                        pstm.setString(j + 1, params[i][j]);
                    }
                }
                pstm.executeUpdate();
            }
            conn.commit();
            return 1;
        } catch (final Exception e) {
            e.printStackTrace();
            try {
                conn.rollback();
            } catch (final Exception e2) {
                e2.printStackTrace();
            }
            return 0;
        } finally {
            close(conn, pstm, null);
        }
    }

    /**
     * 执行SQL语句，返回JSON结果（不带参数）
     */
    public String QueryJson(final String sql) {
        final Connection conn = getConnection();
        Statement stmt;
        try {
            stmt = conn.createStatement();
            final ResultSet rs = stmt.executeQuery(sql);
            final String json = resultSetToJson(rs);
            rs.close();
            stmt.close();
            conn.close();
            return json;
        } catch (final SQLException e) {
            e.printStackTrace();
            return e.getMessage();
        }
    }

    /**
     * 执行SQL语句，返回JSON结果（带参数）
     */
    public String QueryJson(final String sql, final String[] params) {
        Connection conn = null;
        PreparedStatement pstm = null;
        try {
            conn = getConnection();
            pstm = conn.prepareStatement(sql);
            if (params != null) {
                for (int i = 0; i < params.length; i++) {
                    pstm.setString(i + 1, params[i]);
                }
            }
            final ResultSet rs = pstm.executeQuery();
            final String json = resultSetToJson(rs);
            return json;
        } catch (final Exception e) {
            e.printStackTrace();
            return e.toString();
        } finally {
            close(conn, pstm, null);
        }
    }

    public Object ExecuteScalar(final String sql) {
        Object value = null;
        try {
            final RowSet rs = Query(sql);
            if (rs != null) {
                rs.next();
                value = rs.getObject(1);
            }
            return value;
        } catch (final SQLException e) {
            e.printStackTrace();
            return e.getMessage();
        }
    }

    public Object ExecuteScalar(final String sql, final String[] params) {
        Object value = null;
        try {
            final RowSet rs = Query(sql, params);
            if (rs != null) {
                rs.next();
                value = rs.getObject(1);
                return value;
            }
        } catch (final Exception e) {
            return value;
        }
        return value;
    }

    public RowSet Query(final String sql) {
        final Connection conn = getConnection();
        Statement stmt;
        try {
            stmt = conn.createStatement();

            final ResultSet rs = stmt.executeQuery(sql);
            final RowSetFactory factory = RowSetProvider.newFactory();
            final CachedRowSet cachedRs = factory.createCachedRowSet();
            cachedRs.populate(rs);
            rs.close();
            stmt.close();
            conn.close();
            return cachedRs;
        } catch (final SQLException e) {
            e.printStackTrace();
            return null;
        }
    }

    public RowSet Query(final String sql, final String[] params) {
        Connection conn = null;
        PreparedStatement pstm = null;
        try {
            conn = getConnection();
            pstm = conn.prepareStatement(sql);
            if (params != null) {
                for (int i = 0; i < params.length; i++) {
                    pstm.setString(i + 1, params[i]);
                }
            }
            final ResultSet rs = pstm.executeQuery();
            final RowSetFactory factory = RowSetProvider.newFactory();
            final CachedRowSet cachedRs = factory.createCachedRowSet();
            // 使用ResultSet装填RowSet
            cachedRs.populate(rs);
            rs.close();
            pstm.close();
            conn.close();
            return cachedRs;

        } catch (final Exception e) {
            e.printStackTrace();
        } finally {
            close(conn, pstm, null);
        }
        return null;
    }

    /**
     * 执行需要分页的数据库查询操作
     * 
     * @return 查询结果的离线RowSet
     */
    public RowSet Query(final String sql, final String[] params, final Integer pageIndex, final Integer pageSize) {
        Connection conn = null;
        PreparedStatement pstm = null;
        ResultSet rs = null;
        CachedRowSet crs = null;

        try {
            conn = getConnection();
            pstm = conn.prepareStatement(sql, ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
            if (params != null) {
                for (int i = 0; i < params.length; i++) {
                    pstm.setString(i + 1, params[i]);
                }
            }
            rs = pstm.executeQuery();

            // 创建CacheRowSet
            final RowSetFactory factory = RowSetProvider.newFactory();
            crs = factory.createCachedRowSet();
            crs.setPageSize(pageSize);
            crs.populate(rs, (pageIndex - 1) * pageSize + 1);

        } catch (final Exception e) {
            e.printStackTrace();
        } finally {
            close(conn, pstm, rs);
        }

        return crs;
    }

    /**
     * 执行查询的存储过程"{ call addUser(?,?,?,?) }"
     * 
     * @return 返回查询结果的RowSet集合
     */
    public RowSet executeStoredProcedure(final String dsName, final String sp_name, final String[] params) {
        Connection conn = null;
        CallableStatement cstm = null;
        ResultSet rs = null;
        CachedRowSet crs = null;

        try {
            conn = getConnection();
            cstm = conn.prepareCall(sp_name);
            if (params != null) {
                for (int i = 0; i < params.length; i++) {
                    cstm.setString(i + 1, params[i]);
                }
            }
            rs = cstm.executeQuery();

            // 创建CacheRowSet
            final RowSetFactory factory = RowSetProvider.newFactory();
            crs = factory.createCachedRowSet();
            crs.populate(rs);

        } catch (final Exception e) {
            e.printStackTrace();
        } finally {
            close(conn, cstm, rs);
        }

        return crs;
    }

    public void setConnection(final String connection) {
        this._connection = connection;
    }

    public String getUserName() {
        return _userName;
    }

    public void setUserName(final String userName) {
        this._userName = userName;
    }

    public String getPassword() {
        return _password;
    }

    public void setPassword(final String password) {
        this._password = password;
    }

    /**
     * 辅助方法-将ResultSet转换为JSON字符串
     */
    public String resultSetToJson(final ResultSet rs) {
        final org.json.JSONArray array = new org.json.JSONArray();
        ResultSetMetaData metaData;
        try {
            metaData = rs.getMetaData();

            final int columnCount = metaData.getColumnCount();

            while (rs.next()) {
                final JSONObject jsonObj = new JSONObject();

                for (int i = 1; i <= columnCount; i++) {
                    final String columnName = metaData.getColumnLabel(i);
                    final String value = rs.getString(columnName);
                    try {
                        jsonObj.put(columnName, value);
                    } catch (final JSONException e) {
                        e.printStackTrace();
                    }
                }
                array.put(jsonObj);
            }
            final String json = array.toString();
            return json;
        } catch (final SQLException e) {
            e.printStackTrace();

        }
        return "";
    }

    // 查询所有表及注释
    public List<Table> GetTables(String schema) {
        ArrayList<Table> list = new ArrayList<Table>();
        try {
            final String sql = "select TABLE_NAME,TABLE_COMMENT from information_schema.tables where table_schema=?";
            ArrayList<String> parms = new ArrayList<String>();
            parms.add(schema);
            final RowSet rs = Query(sql, parms.toArray(new String[parms.size()]));
            while (rs.next()) {
                final String key = rs.getString("TABLE_NAME").trim() == null ? "" : rs.getString("TABLE_NAME").trim();
                final String val = rs.getString("TABLE_COMMENT") == null ? "" : rs.getString("TABLE_COMMENT").trim();
                Table table = new Table(key, val);
                if (!list.contains(table)) {
                    list.add(table);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();

        }
        return list;
    }

    // 查询指定表字段名及注释
    public List<Field> GetFields(String schema, String tableName) {
        ArrayList<Field> list = new ArrayList<Field>();
        try {
            final String sql = "select COLUMN_NAME, DATA_TYPE,CHARACTER_MAXIMUM_LENGTH,COLUMN_COMMENT,COLUMN_DEFAULT  from information_schema.COLUMNS where table_name =? and table_schema =?";
            final RowSet rs = Query(sql, new String[] {
                    tableName,
                    schema });
            while (rs.next()) {
                final String name = rs.getString("COLUMN_NAME").trim() == null ? ""
                        : rs.getString("COLUMN_NAME").trim();
                final String type = rs.getString("DATA_TYPE") == null ? ""
                        : rs.getString("DATA_TYPE").trim();
                final String length = rs.getString("CHARACTER_MAXIMUM_LENGTH") == null ? ""
                        : rs.getString("CHARACTER_MAXIMUM_LENGTH").trim();
                final String defaul = rs.getString("COLUMN_DEFAULT") == null ? ""
                        : rs.getString("COLUMN_DEFAULT").trim();
                final String comment = rs.getString("COLUMN_COMMENT") == null ? ""
                        : rs.getString("COLUMN_COMMENT").trim();

                Field table = new Field(name, type, length, defaul, comment);
                if (!list.contains(table)) {
                    list.add(table);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();

        }
        return list;
    }

    // 表实体
    public class Table {
        public Table(String key, String val) {
            Name = key;
            Comment = val;
        }

        public String Name;
        public String Comment;
    }

    // 字段实体
    public class Field {
        public Field(String name, String type, String length, String defaul, String comment) {
            Name = name;
            Type = type;
            Length = length;
            Default = defaul;
            Comment = comment;
        }

        public String Name;
        public String Type;
        public String Length;
        public String Comment;
        public String Default;
    }
}

test code

1. Create a test table and write a piece of test data.

--创建测试表
CREATE TABLE `user` (
  `id` int NOT NULL COMMENT '编号',
  `name` varchar(45) DEFAULT '' COMMENT '姓名',
  `age` int DEFAULT '20' COMMENT '年龄',
  `createtime` date DEFAULT NULL COMMENT '创建时间',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb3 COMMENT='用户表';

--写入一条测试数据
insert into user(id,name,age,createtime)values(1,'张三',30,'2023-02-15 09:45')

2. Test the database query. 

Log("【测试访问MySql数据库】");
final String mySqlUrl = "jdbc:mysql://localhost:3306/dbName";
final String mySqlUserName = "root";
final String mySqlPassword = "******";
final MySQLHelper mySql = new MySQLHelper(mySqlUrl, mySqlUserName, mySqlPassword);
final String mySqlScript = "select * from user where name=?";
ArrayList<String> mySqlParms = new ArrayList<String>();
mySqlParms.add("张三");
final String mySqlJson = mySql.QueryJson(mySqlScript, mySqlParms.toArray(new String[mySqlParms.size()]));
Log(mySqlJson + "\n");

List<Table> list = mySql.GetTables("dbName");
	for (Table table : list) {
	Log(table.Name + "-" + table.Comment + "\n");
}
List<Field> fields = mySql.GetFields("dbName","user");
	for (Field field : fields) {
	Log(field.Name + "-" + field.Comment + "\n");
}

Note: JDBC driver (mysql-connector-j-8.0.32.jar) needs to be downloaded by yourself. Download the installation package from the MySQL official website , and you can find the driver package after installation. I installed it under window, you can refer to the following path.