Build Dynamic Query

Use Cases

The following is a code example on how to use Lambda express to build dynamic query the where clause. Here is the use cases:

• client provide a set of query parameters in JSON format or XML format
• Mule flow will transform the request payload to java LinkedHashMap
• We need to write custom transformer to build the database query's where clause
• In the custom transformer, we need to filter the entries with null or empty string value
• The transform should return the string in the format of:
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  1	ID='1243124' and Name='John Smith'

Code Example

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package com.ggl.util;   import java.util.HashMap; import java.util.LinkedHashMap;   public class DynamicQueryBuilder {  public static void main(String[] argv) {   System.out.println("--> Build HashMap Now! <--");   HashMap<string,string> source = new LinkedHashMap<>();   source.put("ID", "123456789");   source.put("NAME", "Gary Liu");   source.put("Address", null);   source.put("Sex", "");       StringBuilder builder = new StringBuilder();       source.entrySet()    .parallelStream()    .filter(e->e.getValue() != null)    .filter(e->e.getValue().length() != 0)    .forEachOrdered(e -> append(builder, e.getKey(), e.getValue()));       String tmpResult = builder.toString();       System.out.println(tmpResult);   System.out.println (tmpResult.replaceFirst(" and " + "$", ""));  }     private static void append(StringBuilder builder, String key, String value) {   builder.append(key + "='" + value + "' and " );  }   }   </string,string>