Admin: 1 версия

2010-06-01T05:05:57Z

1 версия

в 17:44, 31 мая 2010

2010-05-31T17:44:27Z

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== Chaining SQLExceptions ==



<source lang="java">
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
public class Main {
public static void main(String[] args) throws Exception {
try {
Connection conn = getHSQLConnection();
conn.setAutoCommit(false);
Statement st = conn.createStatement();
st.executeUpdate("create table survey (id int,name varchar(30));");
st.executeUpdate("insert into survey (id,name ) values (1,"nameValue")");
st = conn.createStatement();
ResultSet rs = st.executeQuery("SELECT * FROM survey");
outputResultSet(rs);
rs.close();
st.close();
conn.close();
} catch (SQLException sqle) {
do { // loop through each exception
// do something with each exception
System.err.println("Exception occurred:\nMessage: " + sqle.getMessage());
System.err.println("SQL state: " + sqle.getSQLState());
System.err.println("Vendor code: " + sqle.getErrorCode() + "\n----------------");
} while ((sqle = sqle.getNextException()) != null);
}
}
private static void outputResultSet(ResultSet rs) throws Exception {
ResultSetMetaData rsMetaData = rs.getMetaData();
int numberOfColumns = rsMetaData.getColumnCount();
for (int i = 1; i < numberOfColumns + 1; i++) {
String columnName = rsMetaData.getColumnName(i);
System.out.print(columnName + " ");
}
System.out.println();
System.out.println("----------------------");
while (rs.next()) {
for (int i = 1; i < numberOfColumns + 1; i++) {
System.out.print(rs.getString(i) + " ");
}
System.out.println();
}
}
private static Connection getHSQLConnection() throws Exception {
Class.forName("org.hsqldb.jdbcDriver");
String url = "jdbc:hsqldb:mem:data/tutorial";
return DriverManager.getConnection(url, "sa", "");
}
}</source>



== Check for a SQL Warning Using PreparedStatement ==



<source lang="java">
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLWarning;
import java.sql.Statement;
public class Main {
public static void main(String[] args) throws Exception {
Connection conn = getConnection();
conn.setAutoCommit(false);
Statement st = conn.createStatement();
st.executeUpdate("create table survey (id int, name VARCHAR(30) );");
String INSERT_RECORD = "insert into survey(id, name) values(?,?)";
PreparedStatement pstmt = conn.prepareStatement(INSERT_RECORD);
pstmt.setInt(1, 1);
pstmt.setString(2, "name");
pstmt.executeUpdate();
// Get warnings on PreparedStatement object
SQLWarning warning = pstmt.getWarnings();
while (warning != null) {
// Process statement warnings...
String message = warning.getMessage();
String sqlState = warning.getSQLState();
int errorCode = warning.getErrorCode();
warning = warning.getNextWarning();
}
ResultSet rs = st.executeQuery("SELECT * FROM survey");
outputResultSet(rs);
rs.close();
st.close();
conn.close();
}
private static void outputResultSet(ResultSet rs) throws Exception {
ResultSetMetaData rsMetaData = rs.getMetaData();
int numberOfColumns = rsMetaData.getColumnCount();
for (int i = 1; i < numberOfColumns + 1; i++) {
String columnName = rsMetaData.getColumnName(i);
System.out.print(columnName + " ");
}
System.out.println();
System.out.println("----------------------");
while (rs.next()) {
for (int i = 1; i < numberOfColumns + 1; i++) {
System.out.print(rs.getString(i) + " ");
}
System.out.println();
}
}
private static Connection getConnection() throws Exception {
Class.forName("org.hsqldb.jdbcDriver");
String url = "jdbc:hsqldb:mem:data/tutorial";
return DriverManager.getConnection(url, "sa", "");
}
}</source>



== Check for a warning using a Connection object ==



<source lang="java">
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.SQLWarning;
public class Main {
public static void main(String[] args) throws Exception {
try {
Connection conn = getConnection(); // get a java.sql.Connection object
SQLWarning warning = conn.getWarnings();
while (warning != null) {
// process connection warning
String message = warning.getMessage();
String sqlState = warning.getSQLState();
int errorCode = warning.getErrorCode();
warning = warning.getNextWarning();
}
}
catch (SQLException e) {
// ignore the exception
}
finally {
// close JDBC resources: ResultSet, Statement, Connection
}

}
private static Connection getConnection() throws Exception {
Class.forName("org.hsqldb.jdbcDriver");
String url = "jdbc:hsqldb:mem:data/tutorial";
return DriverManager.getConnection(url, "sa", "");
}
}</source>



== Checking for a Warning Using a ResultSet Object ==



<source lang="java">
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.sql.Statement;
public class Main {
public static void main(String[] args) throws Exception {
// Get warnings on ResultSet object
ResultSet rs = null;
Connection conn = null;
Statement stmt = null;
try {
conn = getConnection(); // get a java.sql.Connection object
stmt = conn.createStatement(); // create a statement
// get a result set
String sqlQuery = "select id, name from employees";
rs = stmt.executeQuery(sqlQuery);
while (rs.next()) {
// use result set
//
// get warnings on the current row of the ResultSet object
SQLWarning warning = rs.getWarnings();
if (warning != null) {
// process result set warnings
}
}
} catch (SQLException e) {
// ignore the exception
} finally {
// close JDBC resources: ResultSet, Statement, Connection
}
}
private static Connection getConnection() throws Exception {
Class.forName("org.hsqldb.jdbcDriver");
String url = "jdbc:hsqldb:mem:data/tutorial";
return DriverManager.getConnection(url, "sa", "");
}
}</source>



== Checking for a Warning Using a Statement Object ==



<source lang="java">
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.sql.Statement;
public class Main {
public static void main(String[] args) throws Exception {
// Get warnings on Statement object
Connection conn = null;
Statement stmt = null;
try {
conn = getConnection(); // get a java.sql.Connection object
stmt = conn.createStatement(); // create a statement
// use the statement
// get warnings on Statement object
SQLWarning warning = stmt.getWarnings();
if (warning != null) {
// Process statement warnings
}
} catch (SQLException e) {
// ignore the exception
} finally {
// close JDBC resources: ResultSet, Statement, Connection
}
}
private static Connection getConnection() throws Exception {
Class.forName("org.hsqldb.jdbcDriver");
String url = "jdbc:hsqldb:mem:data/tutorial";
return DriverManager.getConnection(url, "sa", "");
}
}</source>



== Determine Whether a SQL Warning Has Occurred ==

<p>You can check for a warning in three places:</p>



<source lang="java">
The Connection object (java.sql.Connection)
The Statement object (java.sql.Statement)
The ResultSet object (java.sql.ResultSet)</source>



== Exceptions in JDBC ==

<OL><LI>java.sql.SQLException extends the java.lang.Exception class</LI><LI>java.sql.SQLException is a core JDBC exception class that provides information about database access errors and other errors. Most of the JDBC API methods throw SQLException.</LI><LI>java.sql.BatchUpdateException: a BatchUpdateException provides the update counts for all commands that were executed successfully during the batch update.</LI><LI>java.sql.DataTruncation reports a DataTruncation warning (on reads) or throws a DataTruncation exception (on writes) when JDBC unexpectedly truncates a data value.</LI><LI>java.sql.SQLWarning provides information about database access warnings.</LI></OL>

== Extracting Information from SQLException ==



<source lang="java">
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
public class Main {
public static void main(String[] args) throws Exception {
try {
Connection conn = getHSQLConnection();
conn.setAutoCommit(false);
Statement st = conn.createStatement();
st.executeUpdate("create table survey (id int,name varchar(30));");
st.executeUpdate("insert into survey (id,name ) values (1,"nameValue")");
st = conn.createStatement();
ResultSet rs = st.executeQuery("SELECT * FROM survey");
outputResultSet(rs);
rs.close();
st.close();
conn.close();
} catch (SQLException sqle) {
String sqlMessage = sqle.getMessage();
String sqlState = sqle.getSQLState();
int vendorCode = sqle.getErrorCode();
System.err.println("Exception occurred:");
System.err.println("Message: " + sqlMessage);
System.err.println("SQL state: " + sqlState);
System.err.println("Vendor code: " + vendorCode + "\n----------------");
}
}
private static void outputResultSet(ResultSet rs) throws Exception {
ResultSetMetaData rsMetaData = rs.getMetaData();
int numberOfColumns = rsMetaData.getColumnCount();
for (int i = 1; i < numberOfColumns + 1; i++) {
String columnName = rsMetaData.getColumnName(i);
System.out.print(columnName + " ");
}
System.out.println();
System.out.println("----------------------");
while (rs.next()) {
for (int i = 1; i < numberOfColumns + 1; i++) {
System.out.print(rs.getString(i) + " ");
}
System.out.println();
}
}
private static Connection getHSQLConnection() throws Exception {
Class.forName("org.hsqldb.jdbcDriver");
String url = "jdbc:hsqldb:mem:data/tutorial";
return DriverManager.getConnection(url, "sa", "");
}
}</source>



== Get the Details of a SQLException ==



<source lang="java">
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Main {
public static void main(String[] args) throws Exception {
try {
Connection conn = getConnection();
Statement st = conn.createStatement();
st.executeUpdate("create table survey (id int,myDate DATE );");
String INSERT_RECORD = "insert into survey(id, myDate) values(?, ?)";
PreparedStatement pstmt = conn.prepareStatement(INSERT_RECORD);
pstmt.setString(1, "1");
java.sql.Date sqlDate = new java.sql.Date(new java.util.Date().getTime());
pstmt.setDate(2, sqlDate);
pstmt.executeUpdate();
ResultSet rs = st.executeQuery("SELECT * FROM survey");
rs.close();
st.close();
conn.close();
} catch (SQLException e) {
while (e != null) {
String errorMessage = e.getMessage();
System.err.println("sql error message:" + errorMessage);
// This vendor-independent string contains a code.
String sqlState = e.getSQLState();
System.err.println("sql state:" + sqlState);
int errorCode = e.getErrorCode();
System.err.println("error code:" + errorCode);
// String driverName = conn.getMetaData().getDriverName();
// System.err.println("driver name:"+driverName);
// processDetailError(drivername, errorCode);
e = e.getNextException();
}
}
}
private static Connection getConnection() throws Exception {
Class.forName("org.hsqldb.jdbcDriver");
String url = "jdbc:hsqldb:mem:data/tutorial";
return DriverManager.getConnection(url, "sa", "");
}
}</source>



== java.sql.SQLException Methods ==



<source lang="java">
Return Type Method Description
int getErrorCode() Retrieves the vendor-specific exception code for this SQLException object
SQLException getNextException() Retrieves the exception chained to this SQLException object
String getSQLState() Retrieves the SQLState for this SQLException object
void setNextException(SQLException ex) Adds a SQLException object to the end of the chain</source>



== Print the stack trace for a SQLException to STDERR. ==



<source lang="java">
import java.io.PrintWriter;
import java.sql.SQLException;
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*
*/
public class Main {

/**
* Print the stack trace for a SQLException to STDERR.
*
* @param e SQLException to print stack trace of
*/
public static void printStackTrace(SQLException e) {
printStackTrace(e, new PrintWriter(System.err));
}
/**
* Print the stack trace for a SQLException to a
* specified PrintWriter.
*
* @param e SQLException to print stack trace of
* @param pw PrintWriter to print to
*/
public static void printStackTrace(SQLException e, PrintWriter pw) {
SQLException next = e;
while (next != null) {
next.printStackTrace(pw);
next = next.getNextException();
if (next != null) {
pw.println("Next SQLException:");
}
}
}
}</source>



== Print warnings on a Connection to a specified PrintWriter. ==



<source lang="java">
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*
*/
public class Main {

/**
* Print warnings on a Connection to STDERR.
*
* @param conn Connection to print warnings from
*/
public static void printWarnings(Connection conn) {
printWarnings(conn, new PrintWriter(System.err));
}
/**
* Print warnings on a Connection to a specified PrintWriter.
*
* @param conn Connection to print warnings from
* @param pw PrintWriter to print to
*/
public static void printWarnings(Connection conn, PrintWriter pw) {
if (conn != null) {
try {
printStackTrace(conn.getWarnings(), pw);
} catch (SQLException e) {
printStackTrace(e, pw);
}
}
}

/**
* Print the stack trace for a SQLException to a
* specified PrintWriter.
*
* @param e SQLException to print stack trace of
* @param pw PrintWriter to print to
*/
public static void printStackTrace(SQLException e, PrintWriter pw) {
SQLException next = e;
while (next != null) {
next.printStackTrace(pw);
next = next.getNextException();
if (next != null) {
pw.println("Next SQLException:");
}
}
}
}</source>



== Print warnings on a Connection to STDERR. ==



<source lang="java">
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*
*/
public class Main {

/**
* Print warnings on a Connection to STDERR.
*
* @param conn Connection to print warnings from
*/
public static void printWarnings(Connection conn) {
printWarnings(conn, new PrintWriter(System.err));
}
/**
* Print warnings on a Connection to a specified PrintWriter.
*
* @param conn Connection to print warnings from
* @param pw PrintWriter to print to
*/
public static void printWarnings(Connection conn, PrintWriter pw) {
if (conn != null) {
try {
printStackTrace(conn.getWarnings(), pw);
} catch (SQLException e) {
printStackTrace(e, pw);
}
}
}

/**
* Print the stack trace for a SQLException to a
* specified PrintWriter.
*
* @param e SQLException to print stack trace of
* @param pw PrintWriter to print to
*/
public static void printStackTrace(SQLException e, PrintWriter pw) {
SQLException next = e;
while (next != null) {
next.printStackTrace(pw);
next = next.getNextException();
if (next != null) {
pw.println("Next SQLException:");
}
}
}
}</source>



== Use JDBC Chained Exception ==



<source lang="java">
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class ChainedExceptionDemo {
static Connection conn;
public static void main(String[] args) {
String driver = "com.mysql.jdbc.Driver";
String connectionURL = "jdbc:mysql://127.0.0.1:3306/sample";
try {
Class.forName(driver);
} catch (java.lang.ClassNotFoundException e) {
e.printStackTrace();
}
try {
conn = DriverManager.getConnection(connectionURL);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM NONEXISTINGTABLE");
rs.next();
rs.close();
} catch (SQLException sx) {
for (Throwable e : sx) {
System.err.println("Error encountered: " + e);
}
}
}
}</source>



== Using SQLWarning ==



<source lang="java">
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLWarning;
import java.sql.Statement;
public class Main {
public static void main(String[] args) throws Exception {
Connection conn = getHSQLConnection();
conn.setAutoCommit(false);
Statement st = conn.createStatement();
st.executeUpdate("create table survey (id int,name varchar(30));");
st.executeUpdate("insert into survey (id,name ) values (1,"nameValue")");
st = conn.createStatement();
ResultSet rs = st.executeQuery("SELECT * FROM survey");
outputResultSet(rs);
checkForWarning(rs.getWarnings());
rs.close();
st.close();
conn.close();
}
static boolean checkForWarning(SQLWarning w) {
if (w == null) {
return false;
}
do {
System.err.println("Warning:\nMessage: " + w.getMessage());
System.err.println("SQL state: " + w.getSQLState());
System.err.println("Vendor code: " + w.getErrorCode() + "\n----------------");
} while ((w = w.getNextWarning()) != null);
return true;
}
private static void outputResultSet(ResultSet rs) throws Exception {
ResultSetMetaData rsMetaData = rs.getMetaData();
int numberOfColumns = rsMetaData.getColumnCount();
for (int i = 1; i < numberOfColumns + 1; i++) {
String columnName = rsMetaData.getColumnName(i);
System.out.print(columnName + " ");
}
System.out.println();
System.out.println("----------------------");
while (rs.next()) {
for (int i = 1; i < numberOfColumns + 1; i++) {
System.out.print(rs.getString(i) + " ");
}
System.out.println();
}
}
private static Connection getHSQLConnection() throws Exception {
Class.forName("org.hsqldb.jdbcDriver");
String url = "jdbc:hsqldb:mem:data/tutorial";
return DriverManager.getConnection(url, "sa", "");
}
}</source>

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Java Tutorial/Database/SQLException Warning - История изменений

Admin: 1 версия

в 17:44, 31 мая 2010