Java 从多个源读取Spring批处理作业
如何从多个数据库中读取项目?我已经从文件中知道这是可能的。Java 从多个源读取Spring批处理作业,java,database,spring,spring-batch,Java,Database,Spring,Spring Batch,如何从多个数据库中读取项目?我已经从文件中知道这是可能的。 以下示例适用于从多个文件读取 ... <job id="readMultiFileJob" xmlns="http://www.springframework.org/schema/batch"> <step id="step1"> <tasklet> <chunk reader="multiResourceReader" writer="flatFileItem
以下示例适用于从多个文件读取
...
<job id="readMultiFileJob" xmlns="http://www.springframework.org/schema/batch">
<step id="step1">
<tasklet>
<chunk reader="multiResourceReader" writer="flatFileItemWriter"
commit-interval="1" />
</tasklet>
</step>
</job>
...
<bean id="multiResourceReader"
class=" org.springframework.batch.item.file.MultiResourceItemReader">
<property name="resources" value="file:csv/inputs/domain-*.csv" />
<property name="delegate" ref="flatFileItemReader" />
</bean>
...
。。。
...
...
三颗这样的豆子
<bean id="database2" class="org.springframework.batch.item.database.JdbcCursorItemReader">
<property name="name" value="database2Reader" />
<property name="dataSource" ref="dataSource2" />
<property name="sql" value="select image from object where image like '%/images/%'" />
<property name="rowMapper">
<bean class="sym.batch.ImagesRowMapper2" />
</property>
</bean>
没有现成的组件可以执行您的要求;唯一的解决方案是编写一个自定义的
ItemReader
,它委托给JdbcCursorItemReader
(或HibernateCursorItemReader
或任何通用的ItemReader
实现)。您需要准备所有必要的资料(数据源、会话、真正的数据库读取器),并将所有委托读取器绑定到自定义读取器。
编辑: 您需要使用
ItemReader.read()
和mantain reader和delegates状态的循环来模拟作业重启期间的循环
class MyItemReader<T> implements ItemReader<T>, ItemStream {
private ItemReader[] delegates;
private int delegateIndex;
private ItemReader<T> currentDelegate;
private ExecutionContext stepExecutionContext;
public void setDelegates(ItemReader[] delegates) {
this.delegates = delegates;
}
@BeforeStep
private void beforeStep(StepExecution stepExecution) {
this.stepExecutionContext = stepExecution.getExecutionContext();
}
public T read() {
T item = null;
if(null != currentDelegate) {
item = currentDelegate.read();
if(null == item) {
((ItemStream)this.currentDelegate).close();
this.currentDelegate = null;
}
}
// Move to next delegate if previous was exhausted!
if(null == item && this.delegateIndex< this.delegates.length) {
this.currentDelegate = this.delegates[this.currentIndex++];
((ItemStream)this.currentDelegate).open(this.stepExecutionContext);
update(this.stepExecutionContext);
// Recurse to read() to simulate loop through delegates
item = read();
}
return item;
}
public void open(ExecutionContext ctx) {
// During open restore last active reader and restore its state
if(ctx.containsKey("index")) {
this.delegateIndex = ctx.getInt("index");
this.currentDelegate = this.delegates[this.delegateIndex];
((ItemStream)this.currentDelegate ).open(ctx);
}
}
public void update(ExecutionContext ctx) {
// Update current delegate index and state
ctx.putInt("index", this.delegateIndex);
if(null != this.currentDelegate) {
((ItemStream)this.currentDelegate).update(ctx);
}
}
public void close(ExecutionContext ctx) {
if(null != this.currentDelegate) {
((ItemStream)this.currentDelegate).close();
}
}
MyItemReader类实现ItemReader、ItemStream{
私人项目阅读器[]代表;
私有整数委托索引;
私人委托;
私有ExecutionContext步骤ExecutionContext;
公共void集合委托(ItemReader[]委托){
这个。代表=代表;
}
@先于
私有void beforeStep(步骤执行步骤执行){
this.stepExecutionContext=stepExecution.getExecutionContext();
}
公众阅读{
T项=null;
如果(null!=currentDelegate){
item=currentDelegate.read();
if(null==项){
((ItemStream)this.currentDelegate).close();
this.currentDelegate=null;
}
}
//如果上一个代理已用尽,则移动到下一个代理!
if(null==item&&this.delegateIndex
EDIT2:记住设置属性名称;这是让MyItemReader.read()正常工作所必需的
<bean id="itemReader1" class="JdbcCursorItemReader">
<property name="name" value="itemReader1" />
<!-- Set other properties -->
</bean>
我建议使用一种巧妙的方法。如果我们假设一个是mysql数据源的表,该表中的每一行都对应于其他mysql数据源表的行(如位于不同数据源中的联接表),则可以在批处理作业itemreader中执行此操作。例如 Spring数据源配置
<bean id="mySqlDataSource1" class="org.apache.commons.dbcp.BasicDataSource">
<property name="driverClassName" value="${database1.driverClassName}"/>
<property name="url" value="${database1.url}"/>
<property name="username" value="${database1.username}"/>
<property name="password" value="${database1.password}"/>
<property name="validationQuery" value="${database1.validationQuery}"/>
</bean>
<bean id="mySqlDataSource2" class="org.apache.commons.dbcp.BasicDataSource">
<property name="driverClassName" value="${database2.driverClassName}"/>
<property name="url" value="${database2.url}"/>
<property name="username" value="${database2.username}"/>
<property name="password" value="${database2.password}"/>
<property name="validationQuery" value="${database2.validationQuery}"/>
</bean>
您的batch-job.xml
<bean id="multiDatasorceReader" class="org.springframework.batch.item.database.JdbcCursorItemReader" scope="step">
<property name="dataSource" ref="mySqlDataSource1" />
<property name="rowMapper" ref="multiDatasourceRowMapper" />
<property name="sql">
<value>
SELECT * FROM xyz
</value>
</property>
</bean>
<bean id="multiDatasourceRowMapper" class="yourpackage.MultiDatasourceRowMapper" scope="step">
<property name="secondDataSource" ref="mySqlDataSource2" />
<property name="secondSql">
<value>
SELECT * FROM abc
</value>
</property>
</bean>
从xyz中选择*
从abc中选择*
您的RowMapper看起来像
public class MultiDatasourceRowMapper implements RowMapper<String> {
private DataSource secondDataSource;
private String secondSql;
public String mapRow(ResultSet rs, int arg1) throws SQLException {
Connection conn = secondDataSource.getConnection();
PreparedStatement prep = conn.prepareStatement(secondSql);
// Do Something
return "";
}
public void setSecondDataSource(DataSource secondDataSource) {
this.secondDataSource = secondDataSource;
}
public void setSecondSql(String secondSql) {
this.secondSql = secondSql;
}
}
public类MultiDatasourceRowMapper实现行映射器{
私有数据源第二数据源;
私有字符串;
公共字符串mapRow(ResultSet rs,int arg1)引发SQLException{
Connection conn=secondDataSource.getConnection();
PreparedStatement prep=conn.prepareStatement(secondSql);
//做点什么
返回“”;
}
public void setSecondDataSource(数据源第二数据源){
this.secondDataSource=secondDataSource;
}
公共void setSecondSql(字符串secondSql){
this.secondSql=secondSql;
}
}
我建议一种简单的解决方法,它可能不适用于所有情况,但在许多情况下都很有用:
简单定义:
- 2个读卡器,每个数据库一个
- 2步
- 一个包含两个步骤的作业
此设置是否有效取决于处理器和写入程序(在不同步骤中调用时,它们是否仍能正常工作)。在我的例子中,对编写器设置
appendAllowed=true
就足够了,这样两个步骤都可以写入同一个文件。您可以提供更多关于您的情况的信息吗?例如;-您是否从相同的数据库类型(MySQL、Oracle或DB2)读取数据?-你们从不同的数据库实例中读取相同的表吗?若答案是否定的,你们如何将你们的输入映射到相同的对象?MySQL是否有不同的表,我只想取一个字符串
public class MultiDatasourceRowMapper implements RowMapper<String> {
private DataSource secondDataSource;
private String secondSql;
public String mapRow(ResultSet rs, int arg1) throws SQLException {
Connection conn = secondDataSource.getConnection();
PreparedStatement prep = conn.prepareStatement(secondSql);
// Do Something
return "";
}
public void setSecondDataSource(DataSource secondDataSource) {
this.secondDataSource = secondDataSource;
}
public void setSecondSql(String secondSql) {
this.secondSql = secondSql;
}
}