我正在尝试构建一个Java客户端,它连接到客户端的数据库并执行一些查询。
applet需要使用JDBC ...所以我实现了一个非常简单的JDBC连接到位于我的C:/驱动器上的数据库文件。
签署应用程序后(没有签署应用程序,许多安全警报和墙壁)我遇到了这个错误: “此JVM实例中不允许对Applet ID 1进行Liveconnect调用”
有没有人知道一种更简单的流媒体方式,并通过网络浏览器从客户端数据库中获取结果? 或者有谁知道为什么会这样?
我的代码: AppletStart.java(客户端 - 小程序)
public class AppletStart extends Applet {
private static final long serialVersionUID = -2032951133100677643L;
public void queryDatabase(final String databaseFilePath, final String databaseQuery) {
AccessController.doPrivileged(new PrivilegedAction<Object>() {
public Object run() {
JDBCBean jdbcTest = new JDBCBean();
jdbcTest.setDatabaseFilePath(databaseFilePath);
jdbcTest.setDatabaseQuery(databaseQuery);
try {
buildResult(jdbcTest.queryDatabase());
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
});
}
public void buildResult(ResultSet resultSet) throws SQLException {
ResultSetMetaData metaData = resultSet.getMetaData();
int columns = metaData.getColumnCount();
String text = "";
while (resultSet.next()) {
for (int i = 1; i <= columns; ++i) {
text += "" + metaData.getColumnName(i) + ":\t";
text += resultSet.getString(i);
text += "\n";
}
text += "\n";
}
alert(text);
}
public void alert(String text) {
try {
JSObject window = JSObject.getWindow(this);
window.call("showAlert", new Object[] { text });
} catch (JSException jse) {
jse.printStackTrace();
}
}
}
JDBCBean.java(客户端 - 小程序):
public class JDBCBean {
private static String JDBC_DRIVER = "sun.jdbc.odbc.JdbcOdbcDriver";
private static String CONN_STRING_FRAGMENT = "jdbc:odbc:Driver={Microsoft Access Driver (*.mdb)};DBQ=";
private Connection connection;
private Statement statement;
private String databaseFilePath;
private String databaseQuery;
public void setDatabaseFilePath(String databaseFilePath) {
this.databaseFilePath = databaseFilePath;
}
public void setDatabaseQuery(String databaseQuery) {
this.databaseQuery = databaseQuery;
}
public ResultSet queryDatabase() {
try {
Class.forName(JDBC_DRIVER).newInstance();
String connectionString = CONN_STRING_FRAGMENT + databaseFilePath;
connection = DriverManager.getConnection(connectionString, "", "");
buildStatement();
return executeQuery();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
public void buildStatement() throws SQLException {
statement = connection.createStatement();
}
public ResultSet executeQuery() throws SQLException {
boolean foundResults = statement.execute(databaseQuery);
if (foundResults) {
ResultSet set = statement.getResultSet();
if (set != null)
return set;
}
connection.close();
return null;
}
}
HTML(服务器端):
<body onload="queryDatabase()">
<script>
var databaseFilePath = "C:/test_db.mde";
var databaseQuery = "SELECT * FROM test_table";
function showAlert(text) {
alert(text);
}
function queryDatabase() {
document.dbApplet.queryDatabase(databaseFilePath, databaseQuery);
}
</script>
<applet id="dbApplet" code="br.com.applet.AppletStart" archive="../resources/applet/dbapplet.jar" style="width: 1px; height: 1px; float: left;" mayscript="mayscript"></applet>
</body>
答案 0 :(得分:0)
如果您尝试从applet创建到localhost的jdbc连接:只要与本地数据库的连接与applet的远程访问相同(由于安全限制),您应该使用通用规则:
http://www.oracle.com/technetwork/java/dba-140353.html#applet
对于db主机解析 - 如果它不能通过'localhost'或'127.0.0.1'访问,那么你可能应该找到另一种方法来解析本地主机连接路径。
如果您尝试访问文件以进行阅读而不是使用jdbc,那么您也需要为此操作获得授予权限:
http://www.coderanch.com/how-to/java/HowCanAnAppletReadFilesOnTheLocalFileSystem