Outbound Channel Adapter (Outbound Channel Adapter) _ Spring Integration6.2.9中文文档(官方文档中文翻译)|Spring 教程 —

For the latest stable version, please use Spring Integration 6.3.4!spring-doc.cn

The outbound channel adapter is the inverse of the inbound: its role is to handle a message and use it to execute a SQL query. By default, the message payload and headers are available as input parameters to the query, as the following example shows:spring-doc.cn

<int-jdbc:outbound-channel-adapter
    query="insert into items (id, status, name) values (:headers[id], 0, :payload[something])"
    data-source="dataSource"
    channel="input"/>

In the preceding example, messages arriving at the channel labelled input have a payload of a map with a key of something, so the [] operator dereferences that value from the map. The headers are also accessed as a map.spring-doc.cn

The parameters in the preceding query are bean property expressions on the incoming message (not SpEL expressions). This behavior is part of the SqlParameterSource, which is the default source created by the outbound adapter. You can inject a different SqlParameterSourceFactory to get different behavior.

The outbound adapter requires a reference to either a DataSource or a JdbcTemplate. You can also inject a SqlParameterSourceFactory to control the binding of each incoming message to a query.spring-doc.cn

If the input channel is a direct channel, the outbound adapter runs its query in the same thread and, therefore, the same transaction (if there is one) as the sender of the message.spring-doc.cn

Passing Parameters by Using SpEL Expressions

A common requirement for most JDBC channel adapters is to pass parameters as part of SQL queries or stored procedures or functions. As mentioned earlier, these parameters are by default bean property expressions, not SpEL expressions. However, if you need to pass SpEL expression as parameters, you must explicitly inject a SqlParameterSourceFactory.spring-doc.cn

The following example uses a ExpressionEvaluatingSqlParameterSourceFactory to achieve that requirement:spring-doc.cn

<jdbc:outbound-channel-adapter data-source="dataSource" channel="input"
    query="insert into MESSAGES (MESSAGE_ID,PAYLOAD,CREATED_DATE) values (:id, :payload, :createdDate)"
    sql-parameter-source-factory="spelSource"/>

<bean id="spelSource"
      class="o.s.integration.jdbc.ExpressionEvaluatingSqlParameterSourceFactory">
    <property name="parameterExpressions">
        <map>
            <entry key="id"          value="headers['id'].toString()"/>
            <entry key="createdDate" value="new java.util.Date()"/>
            <entry key="payload"     value="payload"/>
        </map>
    </property>
</bean>

For further information, see Defining Parameter Sources.spring-doc.cn

Using the `PreparedStatement` Callback

Sometimes, the flexibility and loose-coupling of SqlParameterSourceFactory does not do what we need for the target PreparedStatement or we need to do some low-level JDBC work. The Spring JDBC module provides APIs to configure the execution environment (such as ConnectionCallback or PreparedStatementCreator) and manipulate parameter values (such as SqlParameterSource). It can even access APIs for low-level operations, such as StatementCallback.spring-doc.cn

Starting with Spring Integration 4.2, MessagePreparedStatementSetter allows the specification of parameters on the PreparedStatement manually, in the requestMessage context. This class plays exactly the same role as PreparedStatementSetter in the standard Spring JDBC API. Actually, it is invoked directly from an inline PreparedStatementSetter implementation when the JdbcMessageHandler invokes execute on the JdbcTemplate.spring-doc.cn

This functional interface option is mutually exclusive with sqlParameterSourceFactory and can be used as a more powerful alternative to populate parameters of the PreparedStatement from the requestMessage. For example, it is useful when we need to store File data to the DataBase BLOB column in a streaming manner. The following example shows how to do so:spring-doc.cn

@Bean
@ServiceActivator(inputChannel = "storeFileChannel")
public MessageHandler jdbcMessageHandler(DataSource dataSource) {
    JdbcMessageHandler jdbcMessageHandler = new JdbcMessageHandler(dataSource,
            "INSERT INTO imagedb (image_name, content, description) VALUES (?, ?, ?)");
    jdbcMessageHandler.setPreparedStatementSetter((ps, m) -> {
        ps.setString(1, m.getHeaders().get(FileHeaders.FILENAME));
        try (FileInputStream inputStream = new FileInputStream((File) m.getPayload()); ) {
            ps.setBlob(2, inputStream);
        }
        catch (Exception e) {
            throw new MessageHandlingException(m, e);
        }
        ps.setClob(3, new StringReader(m.getHeaders().get("description", String.class)));
    });
    return jdbcMessageHandler;
}

From the XML configuration perspective, the prepared-statement-setter attribute is available on the <int-jdbc:outbound-channel-adapter> component. It lets you specify a MessagePreparedStatementSetter bean reference.spring-doc.cn

Batch Update

Starting with version 5.1, the JdbcMessageHandler performs a JdbcOperations.batchUpdate() if the payload of the request message is an Iterable instance. Each element of the Iterable is wrapped to a Message with the headers from the request message if such an element is not a Message already. In the case of regular SqlParameterSourceFactory-based configuration these messages are used to build an SqlParameterSource[] for an argument used in the mentioned JdbcOperations.batchUpdate() function. When a MessagePreparedStatementSetter configuration is applied, a BatchPreparedStatementSetter variant is used to iterate over those messages for each item and the provided MessagePreparedStatementSetter is called against them. The batch update is not supported when keysGenerated mode is selected.spring-doc.cn

Passing Parameters by Using SpEL Expressions

Using the PreparedStatement Callback

Batch Update

Using the `PreparedStatement` Callback