JDBC——数据库连接池以及JDBC代码模版模版

该代码模版由三部分组成，一个是数据库连接池，一个是数据库常用操作的模版抽象，还有一个是重写的连接对象，主要重写关闭连接的方法，将其改为释放到连接池。

OolongConnectionPool.java

package com.oolong.fs.util.db;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.LinkedList;
import java.util.List;

public class OolongConnectionPool {

    private String driverName;
    private String url;
    private String userName;
    private String password;

    private int minConnections = 1;        // 空闲池，最小连接数
    private int maxConnections = 10;    // 空闲池，最大连接数
    private int initConnections = 5;    // 初始化连接数 

    private List<Connection> freeConnections;
    private List<Connection> activeConnections;

    private static OolongConnectionPool pool;
    private static ThreadLocal<Connection> threadLocal = new ThreadLocal<>();  

    public static OolongConnectionPool getInstance() throws Exception {
        if (pool != null) {
            return pool;
        }

        throw new Exception("数据池未初始化");
    }

    public static void init(String driverName, String url, String userName, String password) {
        if (pool == null) {
            pool = new OolongConnectionPool(driverName, url, userName, password);
        }
    }

    private OolongConnectionPool(String driverName, String url, String userName, String password) {
        this.driverName = driverName;
        this.url = url;
        this.userName = userName;
        this.password = password;

        freeConnections = new LinkedList<>();
        activeConnections = new LinkedList<>();

        try {
            Class.forName(driverName);
            Connection conn = null;

            for (int i = 0; i < initConnections; i++) {
                conn = newConnection();
                freeConnections.add(conn);
            }

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private Connection newConnection() throws SQLException {
        Connection conn = DriverManager.getConnection(url, userName, password);
        OolongConnection oolongConn = new OolongConnection(conn, this);
        return oolongConn;
    }

    public synchronized Connection getConnection() {
        Connection conn = null;

        try {
            if (freeConnections.size() > 0) {
                conn = freeConnections.get(0);
                freeConnections.remove(0);
            }

            if (!isValid(conn)) {
                conn = newConnection();
            }
            threadLocal.set(conn);        // 将该连接与当前线程关联
            activeConnections.add(conn);

        } catch (SQLException e) {
            e.printStackTrace();
        }

        return conn;
    }

    public synchronized void releaseConnection(Connection conn) {
        activeConnections.remove(conn);
        threadLocal.remove();
        if (isValid(conn) && freeConnections.size() < maxConnections) {
            freeConnections.add(conn);
        } else {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    public Connection getCurrentConnection() {
        // 默认线程里面取
        Connection conn = threadLocal.get();
        if (!isValid(conn)) {
            conn = getConnection();
        }
        return conn;
    }

    private boolean isValid(Connection conn) {
        try {
            if (conn == null || conn.isClosed()) {
                return false;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return true;
    }
}

DbHelper.java

package com.oolong.fs.util.db;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
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.Types;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.oolong.fs.util.Constant;

public class DbHelper {

    public static List<Map<String, Object>> executeQuery(String sql) {
        return executeQuery(sql, new String[0]);
    }

    public static List<Map<String, Object>> executeQuery(String sql, String[] param) {
        System.out.println(sql);
        Connection conn = null;
        PreparedStatement pst = null;
        ResultSet rs = null;
        List<Map<String, Object>> resut = new ArrayList<>();
        Map<String, Object> map = null;
        try{
            conn = OolongConnectionPool.getInstance().getCurrentConnection();
            pst = conn.prepareStatement(sql);

            for (int i = 0; i < param.length; i++) {
                pst.setString(i+1, param[i]);
            }

            rs = pst.executeQuery();

            ResultSetMetaData rsm = rs.getMetaData();
            String[] columns = new String[rsm.getColumnCount()];

            for (int i = 0; i < rsm.getColumnCount(); i++) {
                columns[i] = rsm.getColumnName(i + 1);
            }

            rs.beforeFirst();

            while(rs.next()) {
                map = new HashMap<>();
                for(String col : columns) {
                    map.put(col, rs.getObject(col));
                }
                resut.add(map);
            }
            rs.close();
            pst.close();
            conn.close();
        } catch (SQLException ex) {
            ex.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return resut;
    }

    public static int executeUpdate(String sql, String[] param) {
        System.out.println(sql);
        Connection conn = null;
        PreparedStatement pst = null;
        int res = 0;

        try{
            conn = OolongConnectionPool.getInstance().getCurrentConnection();
            pst = conn.prepareStatement(sql);

            for (int i = 0; i < param.length; i++) {

                if (Constant.DB_NULL.equals(param[i])) {
                    pst.setNull(i+1, Types.VARCHAR);
                } else {
                    pst.setString(i+1, param[i]);
                }
            }

            res = pst.executeUpdate();

            pst.close();

            // 如果手动管理事务，则连接的关闭在事物管理处手动处理
            if (!conn.getAutoCommit()) {
                conn.close();
            }
        } catch (SQLException ex) {
            ex.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return res;
    }

    public static int batchInsert(String sql, List<String[]> params) {
        System.out.println(sql);
        Connection conn = null;
        PreparedStatement pst = null;
        int res = 0;

        try{
            conn = OolongConnectionPool.getInstance().getCurrentConnection();
            pst = conn.prepareStatement(sql);

            for (String[] param : params) {
                for (int i = 0; i < param.length; i++) {

                    if (Constant.DB_NULL.equals(param[i])) {
                        pst.setNull(i+1, Types.VARCHAR);
                    } else {
                        pst.setString(i+1, param[i]);
                    }
                }
                pst.addBatch();
            }

            pst.executeBatch();

            pst.close();

            // 如果手动管理事务，则连接的关闭在事物管理处手动处理
            if (!conn.getAutoCommit()) {
                conn.close();
            }
        } catch (SQLException ex) {
            ex.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return res;
    }

    public static <T> List<T> fillModel(List<Map<String, Object>> data, Class<T> cls
            , List<String> columns) {

        List<T> res = new ArrayList<>();
        T bean = null;

        try {
            for (Map<String, Object> row : data) {
                bean = cls.newInstance();

                for(String field : columns) {
                    Method method = getMethod(field, cls);
                    method.invoke(bean, row.get(field));
                }
                res.add(bean);
            }

        } catch(Exception e) {
            e.printStackTrace();
        }

        return res;
    }

    private static <T> Method getMethod(String field, Class<T> cls) {

        if (field.startsWith("is")) {
            return getBooleanSetter(field, cls);
        } else {
            return getStringSetter(field, cls);
        }
    }

    /**
     * 到当前类中找setter方法，如果找不到，就到父类中找（针对一般类型）
     * @param field
     * @param cls
     * @return
     */
    private static <T> Method getStringSetter(String field, Class<T> cls) {
        Method method = null;

        try {
            Field property = cls.getDeclaredField(field);
            method = cls.getDeclaredMethod("set"
                + field.substring(0, 1).toUpperCase()
                + field.substring(1), property.getType());

        } catch (NoSuchFieldException e) {
            Class sup = cls.getSuperclass();
            return getStringSetter(field, sup);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return method;
    }

    /**
     * 到当前类中找setter方法，如果找不到，就到父类中找（针对布尔类型）
     * @param field
     * @param cls
     * @return
     */
    private static <T> Method getBooleanSetter(String field, Class<T> cls) {
        Method method = null;

        try {
            Field property = cls.getDeclaredField(field);
            method = cls.getDeclaredMethod("set"
                + field.substring(2, field.length()), property.getType());

        } catch (NoSuchFieldException e) {
            Class sup = cls.getSuperclass();
            return getBooleanSetter(field, sup);

        } catch (Exception e) {
            e.printStackTrace();
        }

        return method;
    }
}

OolongConnection.java

package com.oolong.fs.util.db;

import java.sql.Array;
import java.sql.Blob;
import java.sql.CallableStatement;
import java.sql.Clob;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.NClob;
import java.sql.PreparedStatement;
import java.sql.SQLClientInfoException;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.sql.SQLXML;
import java.sql.Savepoint;
import java.sql.Statement;
import java.sql.Struct;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.Executor;

public class OolongConnection implements Connection {

    private Connection conn;
    private OolongConnectionPool pool;

    public OolongConnection(Connection conn, OolongConnectionPool pool) {
        this.conn = conn;
        this.pool = pool;
    }

    @Override
    public void close() throws SQLException {
        pool.releaseConnection(conn);    // 修改 close() 方法
    }

    @Override
    public boolean isClosed() throws SQLException {
        return conn.isClosed();
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        return conn.unwrap(iface);
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        return conn.isWrapperFor(iface);
    }

    @Override
    public Statement createStatement() throws SQLException {
        return conn.createStatement();
    }

    @Override
    public PreparedStatement prepareStatement(String sql) throws SQLException {
        return conn.prepareStatement(sql);
    }

    @Override
    public CallableStatement prepareCall(String sql) throws SQLException {
        return conn.prepareCall(sql);
    }

    @Override
    public String nativeSQL(String sql) throws SQLException {
        return conn.nativeSQL(sql);
    }

    @Override
    public void setAutoCommit(boolean autoCommit) throws SQLException {
        conn.setAutoCommit(autoCommit);
    }

    @Override
    public boolean getAutoCommit() throws SQLException {
        return conn.getAutoCommit();
    }

    @Override
    public void commit() throws SQLException {
        conn.commit();
    }

    @Override
    public void rollback() throws SQLException {
        conn.rollback();
    }

    @Override
    public DatabaseMetaData getMetaData() throws SQLException {
        return conn.getMetaData();
    }

    @Override
    public void setReadOnly(boolean readOnly) throws SQLException {
        conn.setReadOnly(readOnly);
    }

    @Override
    public boolean isReadOnly() throws SQLException {
        return conn.isReadOnly();
    }

    @Override
    public void setCatalog(String catalog) throws SQLException {
        conn.setCatalog(catalog);
    }

    @Override
    public String getCatalog() throws SQLException {
        return conn.getCatalog();
    }

    @Override
    public void setTransactionIsolation(int level) throws SQLException {
        conn.setTransactionIsolation(level);
    }

    @Override
    public int getTransactionIsolation() throws SQLException {
        return conn.getTransactionIsolation();
    }

    @Override
    public SQLWarning getWarnings() throws SQLException {
        return conn.getWarnings();
    }

    @Override
    public void clearWarnings() throws SQLException {
        conn.clearWarnings();
    }

    @Override
    public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
        return conn.createStatement(resultSetType, resultSetConcurrency);
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency)
            throws SQLException {
        return conn.prepareStatement(sql, resultSetType, resultSetConcurrency);
    }

    @Override
    public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
        return conn.prepareCall(sql, resultSetType, resultSetConcurrency);
    }

    @Override
    public Map<String, Class<?>> getTypeMap() throws SQLException {
        return conn.getTypeMap();
    }

    @Override
    public void setTypeMap(Map<String, Class<?>> map) throws SQLException {
        conn.setTypeMap(map);
    }

    @Override
    public void setHoldability(int holdability) throws SQLException {
        conn.setHoldability(holdability);
    }

    @Override
    public int getHoldability() throws SQLException {
        return conn.getHoldability();
    }

    @Override
    public Savepoint setSavepoint() throws SQLException {
        return conn.setSavepoint();
    }

    @Override
    public Savepoint setSavepoint(String name) throws SQLException {
        return conn.setSavepoint(name);
    }

    @Override
    public void rollback(Savepoint savepoint) throws SQLException {
        conn.rollback(savepoint);
    }

    @Override
    public void releaseSavepoint(Savepoint savepoint) throws SQLException {
        conn.releaseSavepoint(savepoint);
    }

    @Override
    public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability)
            throws SQLException {
        return conn.createStatement(resultSetType, resultSetConcurrency, resultSetHoldability);
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency,
            int resultSetHoldability) throws SQLException {
        return conn.prepareStatement(sql, resultSetType, resultSetConcurrency, resultSetHoldability);
    }

    @Override
    public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency,
            int resultSetHoldability) throws SQLException {
        return conn.prepareCall(sql, resultSetType, resultSetConcurrency, resultSetHoldability);
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
        return conn.prepareStatement(sql, autoGeneratedKeys);
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
        return conn.prepareStatement(sql, columnIndexes);
    }

    @Override
    public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
        return conn.prepareStatement(sql, columnNames);
    }

    @Override
    public Clob createClob() throws SQLException {
        return conn.createClob();
    }

    @Override
    public Blob createBlob() throws SQLException {
        return conn.createBlob();
    }

    @Override
    public NClob createNClob() throws SQLException {
        return conn.createNClob();
    }

    @Override
    public SQLXML createSQLXML() throws SQLException {
        return conn.createSQLXML();
    }

    @Override
    public boolean isValid(int timeout) throws SQLException {
        return conn.isValid(timeout);
    }

    @Override
    public void setClientInfo(String name, String value) throws SQLClientInfoException {
        conn.setClientInfo(name, value);
    }

    @Override
    public void setClientInfo(Properties properties) throws SQLClientInfoException {
        conn.setClientInfo(properties);
    }

    @Override
    public String getClientInfo(String name) throws SQLException {
        return conn.getClientInfo(name);
    }

    @Override
    public Properties getClientInfo() throws SQLException {
        return conn.getClientInfo();
    }

    @Override
    public Array createArrayOf(String typeName, Object[] elements) throws SQLException {
        return conn.createArrayOf(typeName, elements);
    }

    @Override
    public Struct createStruct(String typeName, Object[] attributes) throws SQLException {
        return conn.createStruct(typeName, attributes);
    }

    @Override
    public void setSchema(String schema) throws SQLException {
        conn.setSchema(schema);
    }

    @Override
    public String getSchema() throws SQLException {
        return conn.getSchema();
    }

    @Override
    public void abort(Executor executor) throws SQLException {
        conn.abort(executor);
    }

    @Override
    public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {
        conn.setNetworkTimeout(executor, milliseconds);
    }

    @Override
    public int getNetworkTimeout() throws SQLException {
        return conn.getNetworkTimeout();
    }

}

使用之前需要先初始化连接池：

OolongConnectionPool.init("com.mysql.jdbc.Driver"
                , "jdbc:mysql://localhost:3306/fileshare?useSSL=true"
                , "root", "123");

下面是一些具体调用的示例：

package com.oolong.fs.file.dao.impl;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import com.oolong.fs.file.dao.ProjectDao;
import com.oolong.fs.file.dao.condition.ProjectCondition;
import com.oolong.fs.file.model.ProjectModel;
import com.oolong.fs.util.Constant;
import com.oolong.fs.util.StringUtil;
import com.oolong.fs.util.db.DbHelper;

public class ProjectDaoImpl implements ProjectDao {

    private static String columnStr;
    private static List<String> columns;
    private static String table = "t_file_project";

    static {
        columns = new ArrayList<>();
        columns.add("wid");
        columns.add("name");
        columns.add("description");
        columns.add("createUser");
        columns.add("createTime");
        columns.add("parentWid");
        columns.add("scope");
        columns.add("status");

        columnStr = String.join(",", columns);
    }

    @Override
    public List<ProjectModel> findByCondition(ProjectCondition condition) {
        List<String> params = new ArrayList<>();

        StringBuilder sql = new StringBuilder();
        sql.append(Constant.SQL_SELECT).append(columnStr).append(" FROM ")
                .append(table).append(Constant.SQL_WHERE);

        buildScopeCondition(sql, params, condition);
        buildParentCondition(sql, params, condition);
        buildStatusCondition(sql, params, condition);
        buildCreateUserCondition(sql, params, condition);
        buildKeyworkCondition(sql, params, condition);

        sql.append("1 = 1");

        String[] par = new String[params.size()];

        for (int i = 0; i < params.size(); i++) {
            par[i] = params.get(i);
        }

        List<Map<String, Object>> res = DbHelper.executeQuery(sql.toString(), par);
        List<ProjectModel> models = DbHelper.fillModel(res, ProjectModel.class, columns);
        return models;
    }

    private void buildScopeCondition(StringBuilder sql, List<String> params, ProjectCondition condition) {
        if (!condition.isAdmin() && !(condition.getScope() < 0)) {
            sql.append("scope = ?").append(Constant.SQL_AND);
            params.add(condition.getScope() + "");
        }
    }

    private void buildParentCondition(StringBuilder sql, List<String> params, ProjectCondition condition) {
        if (!StringUtil.isEmpty(condition.getParentWid())) {
            sql.append("parentWid = ?").append(Constant.SQL_AND);
            params.add(condition.getParentWid());
        }
    }

    private void buildStatusCondition(StringBuilder sql, List<String> params, ProjectCondition condition) {
        if (!(condition.getStatus() < 0)) {
            sql.append("status = ?").append(Constant.SQL_AND);
            params.add(condition.getStatus() + "");
        }
    }

    private void buildCreateUserCondition(StringBuilder sql, List<String> params, ProjectCondition condition) {
        if (!StringUtil.isEmpty(condition.getCreateUser())) {
            sql.append("createUser = ?").append(Constant.SQL_AND);
            params.add(condition.getCreateUser());
        }
    }

    private void buildKeyworkCondition(StringBuilder sql, List<String> params, ProjectCondition condition) {
        if (!StringUtil.isEmpty(condition.getKeyword())) {
            sql.append("(");

            sql.append("name like ?").append(Constant.SQL_OR);
            params.add("%" + condition.getKeyword() + "%");

            sql.append("description like ?");
            params.add("%" + condition.getKeyword() + "%");

            sql.append(")").append(Constant.SQL_AND);
        }
    }

    @Override
    public List<ProjectModel> findByWids(boolean isIn, List<String> wids) {

        StringBuilder sql = new StringBuilder();
        sql.append(Constant.SQL_SELECT).append(columnStr).append(" FROM ")
                .append(table).append(Constant.SQL_WHERE);

        if (isIn) {
            sql.append("wid in ('");
        } else {
            sql.append("wid not in ('");
        }

        sql.append(String.join("','", wids)).append("')");

        System.out.println(sql.toString());

        List<Map<String, Object>> res = DbHelper.executeQuery(sql.toString());
        List<ProjectModel> models = DbHelper.fillModel(res, ProjectModel.class, columns);
        return models;
    }

    @Override
    public List<ProjectModel> fingParticipantProjectsByUserWid(String userWid) {
        String sql = Constant.SQL_SELECT + columnStr + " FROM " + table + " where wid = "
                + "(SELECT projectWid FROM fileshare.t_file_member where userWid= ? )";
        List<Map<String, Object>> res = DbHelper.executeQuery(sql, new String[]{userWid});
        List<ProjectModel> models = DbHelper.fillModel(res, ProjectModel.class, columns);
        return models;
    }

    @Override
    public ProjectModel findByWid(String wid) {
        String sql = Constant.SQL_SELECT + columnStr + " FROM " + table + " where wid = ?";
        List<Map<String, Object>> res = DbHelper.executeQuery(sql, new String[]{wid});
        List<ProjectModel> models = DbHelper.fillModel(res, ProjectModel.class, columns);
        return models.size() > 0 ? models.get(0) : null;
    }

    @Override
    public int insert(ProjectModel model) {
        String sql = Constant.SQL_INSERT + table + " (" + columnStr.replace("createTime,", "")
                + ") VALUES (?, ?, ?, ?, ?, ?, ?)";
        String[] param = new String[]{
                model.getWid(), model.getName(), model.getDescription(),
                model.getCreateUser(), model.getParentWid(), model.getScope() + "",
                model.getStatus() + ""
        };
        return DbHelper.executeUpdate(sql, param);
    }

    @Override
    public int update(ProjectModel model) {
        StringBuilder sql = new StringBuilder();
        List<String> params = new ArrayList<>();
        sql.append(Constant.SQL_UPDATE).append(table).append(" SET ");

        if (!StringUtil.isEmpty(model.getName())) {
            sql.append("name = ?").append(Constant.SQL_COMMA);
            params.add(model.getName());
        }

        if (!StringUtil.isEmpty(model.getDescription())) {
            sql.append("description = ?").append(Constant.SQL_COMMA);;
            params.add(model.getDescription());
        }

        if (model.getScope() >= 0) {
            sql.append("scope = ?").append(Constant.SQL_COMMA);
            params.add(model.getScope() + "");
        }

        if (model.getStatus() >= 0 ) {
            sql.append("status = ?").append(Constant.SQL_COMMA);
            params.add(model.getStatus() + "");
        }

        if (!StringUtil.isEmpty(model.getParentWid())) {
            sql.append("parentWid = ?");
            params.add(model.getParentWid());
        }

        sql.append(Constant.SQL_WHERE).append("wid = ?");
        params.add(model.getWid());

        String[] par = new String[params.size()];
        for (int i = 0; i < params.size(); i++) {
            par[i] = params.get(i);
        }

        return DbHelper.executeUpdate(sql.toString(), par);
    }

    @Override
    public int delete(String wid) {
        //逻辑删除
        String sql = Constant.SQL_UPDATE + table + " SET  status =1 "+" where wid = ?";
        String[] params = new String[]{wid};

        return DbHelper.executeUpdate(sql, params);
    }

    @Override
    public List<String> FindRoleWidsByUserWid(String userWid) {
        String sql = Constant.SQL_SELECT + "roleWid FROM t_auth_rel_role_usergroup where usergroupWid in ("
                +Constant.SQL_SELECT + "groupWid FROM t_auth_rel_user_group where userWid = ? )";
        List<Map<String, Object>> res = DbHelper.executeQuery(sql, new String[]{userWid});
        List<String> result = new ArrayList<>();
        for (Map<String, Object> re : res) {
            for (Map.Entry<String, Object> r : re.entrySet()) {
               result = (List<String>) r.getValue();
            }
        }

        return result;
    }

    @Override
    public List<ProjectModel> findAll() {
        String sql = Constant.SQL_SELECT + columnStr + " FROM " + table ;
        List<Map<String, Object>> res = DbHelper.executeQuery(sql);
        List<ProjectModel> projects = DbHelper.fillModel(res, ProjectModel.class, columns);
        return projects;
    }

}