Java template method pattern example 2018-01-25 02:15
Template method pattern is commonly used in this scenario that main logic is stable but sub steps are not. Let's say you want to add export function in your system. For different data source there are different way to export data, but the main steps are the same: "getData", "processData" and "export". Let's try to use template method pattern in this example.
package structure
Client and exporters are NOT in same package.
├─template
│ │ Client.java
│ │
│ └─exporter
│ AbstractExporter.java
│ ExporterFromDB.java
AbstractExporter
package template.exporter;
import java.util.List;
public abstract class AbstractExporter {
public void exportData() {
List<String> data = getData();
String processedData = processData(data);
export(processedData);
}
protected abstract List<String> getData();
protected abstract String processData(List<String> data);
protected abstract void export(String sumData);
}
ExporterFromDB
package template.exporter;
import java.util.Arrays;
import java.util.List;
public class DBExporter extends AbstractExporter {
@Override
protected List<String> getData() {
List<String> data = Arrays.asList("data1", "data2", "data3");
System.out.println("select data from database:" + data);
return data;
}
@Override
protected String processData(List<String> data) {
System.out.println("process data:split all data by ';' ");
return String.join(";", data);
}
@Override
protected void export(String sumData) {
System.out.println("print:" + sumData);
}
}
Client
package template;
import template.exporter.AbstractExporter;
import template.exporter.DBExporter;
public class Client {
public static void main(String[] args) {
AbstractExporter exporter = new DBExporter();
exporter.exportData();
}
}
The output is like following.
select data from database:[data1, data2, data3]
process data:split all data by ';'
print:data1;data2;data3
EOF