wandermonk :
I have a requirement to parse a text file and generate JSON document. The text file has a pattern of text which contains a key which is a name and the value is a huge text of TSV with headers.
I could parse the text file and generate bean classes using the headers and now i want to set the data to this generated bean class. I am using reflection to do this.
Class<?> beanClass = BeanClassGenerator.beanGenerator(k, mapForBeanGeneration);
try {
Object beanClassObject = beanClass.newInstance();
lines.forEach(line -> {
if (line != null && !line.isEmpty() && !line.equals("null")) {
String[] lineData = line.split("\t");
System.out.println("LineData length :: " + lineData.length);
Method[] methods = beanClass.getMethods();
System.out.println("Methods length :: " + methods.length);
int index = 0;
for (Method m : methods) {
m.setAccessible(true);
if (m.getName().startsWith("set")) {
try {
if ((lineData.length <= index) && lineData[index] != null) {
m.invoke(beanClassObject, lineData[index]);
index++;
} else {
m.invoke(beanClassObject, " ");
}
} catch (IllegalAccessException | InvocationTargetException e) {
e.printStackTrace();
}
}
}
}
});
ObjectMapper om = new ObjectMapper();
System.out.println(om.writeValueAsString(beanClassObject));
} catch (InstantiationException | IllegalAccessException | JsonProcessingException e) {
e.printStackTrace();
}});
The problem with the approach is that most of the times all the column values may not have data it can be nulled.
I am wondering if there is an easier way of doing this. Any help is appreciated.
Here is the bean generation method.
public static Class<?> beanGenerator(final String className, final Map<String, Class<?>> properties) {
BeanGenerator beanGenerator = new BeanGenerator();
beanGenerator.setNamingPolicy(new NamingPolicy() {
@Override
public String getClassName(String prefix, String source, Object key, Predicate names) {
return className;
}
});
BeanGenerator.addProperties(beanGenerator, properties);
return (Class<?>) beanGenerator.createClass();
}
Here is the sample text file which needs to be converted to the JSON output.
<Data1>
Col1 col2 col3 col4 col5
even sense met has
root greatest spin mostly
gentle held introduced palace
cold equator remember grandmother
slightly butter depth like
distant second coast everyone
<Data2>
Col1 col2 col3 col4 col5 col6 col7 col8
greatest rope operation flies brown continent combination read
slightly diagram he grandfather where party fifty pour
well put plastic anyway refer careful correct furniture
how since army tongue birthday been clock official
table command specific distant cutting hill movie experience
national though stopped youth army underline five know
<Data3>
Col1 col2 col3 col4 col5 col6 col7 col8 col9 col9 col10
vessels characteristic ship joy than tomorrow high seven future trade
try gray fourth advice week stream motion musical whom tin
limited daughter large rice came home chicken wheat engine box
easy city pair strange stage visitor coach announced allow simple
jet therefore single during construction flag bigger muscle complex pleasure
income several coat range dull cattle damage jump present shake
JSON output:
[{
"<Data1>": [{
"col1": "",
"col2": "",
"col3": "",
"col4": ""
},
{
"col1": "",
"col2": "",
"col3": "",
"col4": ""
},
{
"col1": "",
"col2": "",
"col3": "",
"col4": ""
}
]
}, {
"<Data2>": [{
"col1": "",
"col2": "",
"col3": "",
"col4": "",
"col5": "",
"col6": "",
"col7": "",
"col8": ""
},
{
"col1": "",
"col2": "",
"col3": "",
"col4": "",
"col5": "",
"col6": "",
"col7": "",
"col8": ""
},
{
"col1": "",
"col2": "",
"col3": "",
"col4": "",
"col5": "",
"col6": "",
"col7": "",
"col8": ""
}
]
}]
I came up with a solution using the Maps.
Map<String, List<Map<String, String>>> finalMap = new HashMap<>();
metadataMap.forEach((k, v) -> {
List<Map<String, String>> datamap = new ArrayList<>();
String key = k;
String[] fields = v.getFields();
List<String> lines = v.getLines();
lines.forEach(line -> {
if (line != null && !line.isEmpty() && !line.equals("null")) {
String[] fieldData = line.split("\t");
Map<String, String> eachLineMap = new HashMap<>();
for (int index = 0; index < fields.length; index++) {
if (index < fieldData.length && (fieldData[index] != null && !fieldData[index].isEmpty())) {
eachLineMap.put(fields[index], fieldData[index]);
} else {
eachLineMap.put(fields[index], " ");
}
datamap.add(eachLineMap);
}
}
});
finalMap.put(key, datamap);
});
try {
output = new ObjectMapper().writeValueAsString(finalMap);
}catch(JsonProcessingException e){
e.printStackTrace();
}
wandermonk :
I realized that instead of creating the POJOs with a complex approach. It is better to use the Maps and convert them to JSON using Jackson ObjectMapper. Posting for others who think this might be a useful approach.
public String convert(Map<String, ? extends Metadata> metadataMap) {
String output = "";
Map<String, List<Map<String, String>>> finalMap = new HashMap<>();
metadataMap.forEach((k, v) -> {
List<Map<String, String>> datamap = new LinkedList<>();
String key = k;
String[] fields = v.getFields();
List<String> lines = v.getLines();
lines.forEach(line -> {
if (line != null && !line.isEmpty() && !line.equals("null")) {
String[] fieldData = line.split("\t",-1);
Map<String, String> eachLineMap = new HashMap<>();
for (int index = 0; index < fields.length; index++) {
if (index < fieldData.length && (fieldData[index] != null && !fieldData[index].isEmpty())) {
eachLineMap.put(fields[index], fieldData[index]);
} else {
eachLineMap.put(fields[index], " ");
}
datamap.add(eachLineMap);
}
}
});
finalMap.put(key, datamap);
});
try {
output = new ObjectMapper().writeValueAsString(finalMap);
}catch(JsonProcessingException e){
e.printStackTrace();
}
return output;
}