Merge pull request #9256 from taosdata/zyyang-taosdata-patch-9

set-client-parameter

documentation20/cn/08.connector/01.java/docs.md

@@ -594,6 +594,65 @@ public void setString(int columnIndex, ArrayList<String> list, int size) throws
 public void setNString(int columnIndex, ArrayList<String> list, int size) throws SQLException
 ```
 
+### <a class="anchor" id="set-client-configuration"></a>设置客户端参数
+从TDengine-2.3.5.0版本开始，jdbc driver支持在应用的第一次连接中，设置TDengine的客户端参数。Driver支持JDBC-JNI方式中，通过jdbcUrl和properties两种方式设置client parameter。
+注意：
+* JDBC-RESTful不支持设置client parameter的功能。
+* 应用中设置的client parameter为进程级别的，即如果要更新client的参数，需要重启应用。这是因为client parameter是全局参数，仅在应用程序的第一次设置生效。
+* 以下示例代码基于taos-jdbcdriver-2.0.36。
+
+示例代码：
+```java
+public class ClientParameterSetting {
+    private static final String host = "127.0.0.1";
+ 
+    public static void main(String[] args) throws SQLException {
+        setParameterInJdbcUrl();
+ 
+        setParameterInProperties();
+    }
+ 
+    private static void setParameterInJdbcUrl() throws SQLException {
+        String jdbcUrl = "jdbc:TAOS://" + host + ":6030/?debugFlag=135&asyncLog=0";
+ 
+        Connection connection = DriverManager.getConnection(jdbcUrl, "root", "taosdata");
+ 
+        printDatabase(connection);
+ 
+        connection.close();
+    }
+ 
+    private static void setParameterInProperties() throws SQLException {
+        String jdbcUrl = "jdbc:TAOS://" + host + ":6030/";
+        Properties properties = new Properties();
+        properties.setProperty("user", "root");
+        properties.setProperty("password", "taosdata");
+        properties.setProperty("debugFlag", "135");
+        properties.setProperty("asyncLog", "0");
+        properties.setProperty("maxSQLLength", "1048576");
+ 
+        try (Connection conn = DriverManager.getConnection(jdbcUrl, properties)) {
+            printDatabase(conn);
+        }
+    }
+ 
+    private static void printDatabase(Connection connection) throws SQLException {
+        try (Statement stmt = connection.createStatement()) {
+            ResultSet rs = stmt.executeQuery("show databases");
+ 
+            ResultSetMetaData meta = rs.getMetaData();
+            while (rs.next()) {
+                for (int i = 1; i <= meta.getColumnCount(); i++) {
+                    System.out.print(meta.getColumnLabel(i) + ": " + rs.getString(i) + "\t");
+                }
+                System.out.println();
+            }
+        }
+    }
+}
+```
+
+
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