您可以自定义Jackson如何缩进输出。根据您使用的Jackson版本，有多种实现方法。
杰克逊2.5及更高版本
请执行下列操作：
DefaultPrettyPrinter printer = new DefaultPrettyPrinter();Indenter indenter = new DefaultIndenter();printer.indentObjectsWith(indenter); // Indent JSON objectsprinter.indentArraysWith(indenter); // Indent JSON arraysObjectMapper mapper = new ObjectMapper();mapper.writer(printer).writevalue(new FileOutputStream(outputFile), node);
默认情况下，将使用2个空格。对于不同数量的空格，请使用
DefaultIndenter接收字符串以缩进级别和行分隔符的构造函数：
Indenter indenter = new DefaultIndenter(" ", DefaultIndenter.SYS_LF);杰克逊2.4及更低版本
请执行下列操作：
DefaultPrettyPrinter printer = new DefaultPrettyPrinter();Indenter indenter = new Lf2SpacesIndenter();printer.indentObjectsWith(indenter); // Indent JSON objectsprinter.indentArraysWith(indenter); // Indent JSON arraysObjectMapper mapper = new ObjectMapper();mapper.writer(printer).writevalue(new FileOutputStream(outputFile), node);
将
Lf2SpacesIndenter被限制在2个空格，你不能改变它。
如果需要不同数量的空格，则需要编写自定义实现。这是使用与
DefaultIndenterJackson
2.5中引入的代码相同的代码的代码：
public class CustomSpaceIndenter extends DefaultPrettyPrinter.NopIndenter { public final static String SYS_LF; static { String lf; try { lf = System.getProperty("line.separator"); } catch (Throwable t) { lf = "n"; // fallback when security manager denies access } SYS_LF = lf; } public static final CustomSpaceIndenter SYSTEM_LINEFEED_INSTANCE = new CustomSpaceIndenter(" ", SYS_LF); private final static int INDENT_LEVELS = 16; private final char[] indents; private final int charsPerLevel; private final String eol; public CustomSpaceIndenter() { this(" ", SYS_LF); } public CustomSpaceIndenter(String indent, String eol) { charsPerLevel = indent.length(); indents = new char[indent.length() * INDENT_LEVELS]; int offset = 0; for (int i=0; i<INDENT_LEVELS; i++) { indent.getChars(0, indent.length(), indents, offset); offset += indent.length(); } this.eol = eol; } public CustomSpaceIndenter withLinefeed(String lf) { if (lf.equals(eol)) { return this; } return new CustomSpaceIndenter(getIndent(), lf); } public CustomSpaceIndenter withIndent(String indent) { if (indent.equals(getIndent())) { return this; } return new CustomSpaceIndenter(indent, eol); } public String getEol() { return eol; } public String getIndent() { return new String(indents, 0, charsPerLevel); } @Override public boolean isInline() { return false; } @Override public void writeIndentation(JsonGenerator jg, int level) throws IOException { jg.writeRaw(eol); if (level > 0) { // should we err on negative values (as there's some flaw?) level *= charsPerLevel; while (level > indents.length) { // unlike to happen but just in case jg.writeRaw(indents, 0, indents.length); level -= indents.length; } jg.writeRaw(indents, 0, level); } }}可以如下使用：
Indenter indenter = new CustomSpaceIndenter(" ", CustomSpaceIndenter.SYS_LF);
