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;

/** java.sql.Connection proxy source*/
public abstract class ProxyConnectionBase implements Connection {
    protected Connection conn;
    public ProxyConnectionBase(Connection conn){
        this.conn = conn;
    }

    /** {@inheritDoc} */
    @Override
    @SuppressWarnings("unchecked")
    public final <T> T unwrap(Class<T> iface) throws SQLException {
        if (iface.isInstance(conn)) {
            return (T) conn;
        } else {
        	throw new SQLException("`" + iface + "`I can't seem to cast to.");
        }
    }

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

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

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

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

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

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

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

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

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

    /** {@inheritDoc} */
    @Override
    public void close() throws SQLException {
        conn.close();
    }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

e? what's this? ?? ??

You might think, but it's convenient. this. Everyone, please try to predict the usage.

Or rather, the title says proxy

That's right. This is the "Proxy Element" series that makes it easy to create a proxy. Then, sql received from java.sql.Connection # prepareStatement Let's create a proxy that outputs to the console.

/**Proxy that outputs SQL to the console*/
public class ProxyConnection extends ProxyConnectionBase{
	public ProxyConnection(Connection arg0) {
		super(arg0);
	}
    /** {@inheritDoc} */
    @Override
    public PreparedStatement prepareStatement(String sql) throws SQLException {
    	System.out.println(sql);
        return conn.prepareStatement(sql);
    }
}

It's easy! After that, java.sql.Connection connection = new ProxyConnection (connection); You can use it just by wrapping it with.

By the way, using java.lang.reflect.Proxy as in the following article, You can also programmatically create a proxy. Proxy for logging SQL and SQL results -Qiita

java.sql.Connection Proxy source

e? what's this? ?? ??

Or rather, the title says proxy